Remove the incomplete Firefox extension

A recent successful prototype of a Firefox extension
based on the new WebExtensions API highlighted that as
the way forwards for Hypothesis on Firefox, as it lets
us offer feature parity with much easier maintenance.

If we decide that we want to support the extension for Firefox pre-45, we may
do that by shimming the Chrome APIs using the JPM SDK APIs, similar
to what https://github.com/einaregilsson/Redirector have done.

This commit removes the legacy incomplete
Firefox extension which is missing all of the recent improvements
and tests for the Chrome extension.

Move configuration of ES index into search

Use raven-js for client-side error capture and reporting

For browsers that support it (currently only Chrome >= 49),
catch unhandled promise rejections and report them to Sentry.

This also fixes an issue with incorrect subclassing of
the base Error type in errors.js

Strip Via prefixes in URL normalization

Add a small hysteresis threshold for annotation quotes

If an annotation quote requires 2 or 3 lines of text, it will
not be truncated, otherwise it will be truncated to 2 lines.

Capture exceptions reported via Angular's $exceptionHandler
service and window.onerror and report them via Raven.

The client currently uses the same Sentry DSN as the main
application, which gets the DSN from the SENTRY_DSN
environment variable.

 * Add a <script> tag to all pages on the site which
   defines a window.RAVEN_CONFIG variable which provides the DSN
   and release string needed to configure Raven JS on the client

 * Configure and setup RavenJS in the main site JS, Chrome
   extension and the sidebar.

   For the sidebar, Angular integration is configured
   using Raven's Angular plugin.

 * Configure the user ID associated with Sentry reports
   when the session state is received

 * Extract the code which builds the sidebar/extension
   config dictionary out of the template into
   its own module for easier sharing between the Chrome
   extension and the sidebar's code.

Implement a hysteresis threshold in excerpts

Allow the excerpt's contents to exceed the collapsed
height by a threshold set with the 'overflow-hystersis' attribute
before the excerpt's contents are truncated.

This fixes a problem where the contents of an annotation
body could exceed the threshold by only a couple of pixels,
resulting in a 'More' link which resulted in only half a line
of extra text being revealed.

Fix annotation thread collapsing

This makes it possible to unit test it easily

As far as I can tell this $watch() doesn't do anything. Its purpose
appears to be to uncollapse a thread if that thread contains an
annotation that's being edited. But after deleting it, that uncollapsing
still seems to happen (for example: edit an annotation but don't save or
cancel it yet, change to another group, change back to the first group -
the thread containing the annotation you were editing is uncollapsed).

This code was added before the groups feature existed, so I don't know
what use-case it was intended for.

This was broken by all the recent annotation directive refactoring:
annotation threads are now shown uncollapsed by default (should be
collapsed) and the buttons to collapse/uncollapse them do nothing.

vm/ctrl.editing became a method vm/ctrl.editing() but some code in the
link function wasn't updated.

This fixes them to be collapsed by default and gets the
collapse/uncollapse buttons working but I'm not sure if the collapse
behaviour is correct with nested threads.

Fixes #2823.

Refactor badge count fetching in Chrome extension

Paginate groups admin

Add "create account or sign in" banner

Show correct hostname in 'Add to your site' instructions

Fix warnings during client test execution

Also remove the "Sign in / Create an account" tabs from the "sign in"
panel. They're no longer needed because the new "To annotate this
document create a free account or sign in" banner to the top of the
sidebar has both links.

Also add a "Sign up" link to the top bar.

Faster docker builds

Show the annotation's group not the focused group

Fill hole in groups dropdown button

Work around a bug in Chrome, see
https://gist.github.com/robertknight/8450c09b280564df03f9#file-transform-inline-click-bug-html

Fixes #2852.

In AnnotationController use domainModel.group instead of
groups.focused() to determine which group to display on the annotation.

groups.focused() works fine as long as the group that the annotation
belongs to is always the currently focused group. This is true when in
the sidebar, but not on the stream or on individual annotation pages. On
those pages the most recently focused group the last time the sidebar
was shown is displayed on every annotation, instead of the actual groups
of the annotations.

This means that we now need to update the domainModel.group of new
annotations when the focused group changes, to support this use:

1. Create a new annotation but don't click save yet
2. Change the focused group
3. Save the annotation

The annotation is correctly saved with the currently (and not the
previously) focused group, and also after the focused group the name of
the newly focused group is displayed on the annotation before it's
saved.

Fixes #2839.

Merge pull request #2849 from hypothesis/2848-TypeError-Cannot-read-property-show_sidebar_tutorial-of-undefined

Don't crash if session.state is {}

Fix "angular not defined" crash

This was preventing the sidebar from loading.

Fixes #2848.

Fix #2845 unsafe eval on GitHub

Don't use the node module 'has', it requires 'function-bind' which does
the equivalent of an eval() which doesn't work with some
Content Security Policies.

Fixes #2845.

We don't have (or need) the "isarray" module in our dependencies

 * Wrap error reporting of sidebar injection failures
   so that we can stub it during tests and in future
   get them reported back to us

 * Silence warnings about WebSocket disconnections during
   the socket test.

 * Disallow console warnings during tests. In future it is likely
   that we may end up wrapping console reporting from the main app
   in the same way as in the Chrome extension but for the moment
   it is still useful to log exceptional issues

Add a dismissable tutorial in the sidebar