Instead we use a method on the scope to determine the current
permission level.

Focus share link when pop-up opens

Sticky privacy on the browser

Use an object for privacy level models

Provide a feedback button in the interface

This makes the association between the level key name and the display
text explicit and tight in the code.

Meant to resolve #1653. As per @dwhly's suggestion the dropdown menu is now accessible even when not logged in. Note: items relevant to only logged in users are not shown.

Restructure Chrome Extension

- The permission plugin no longer sets the permissions
- Read permission is a one-item list ["group:__world__"] instead of ["group:__world__", <username>"]
- Privacy directive moved to directives/privacy.coffee
- Uses the simple localStorage solution inside the privacy directive.

Consistent names for focusing on annotations.

Remove some dead code

Improve visual diff code

Remove the gray background from annotation cards on hover.

 - Simplify a check for an error condition
 - Add a test case to avoid regressing the same error

As discussed in #1634

When creating a reply, there was an exception
on the console, because the target list is empty,
and some code was not prepared for that.

This takes care of that.

Fix #1661

[WIP] Restore feature to scroll for annotations

Reposition and style show differences checkbox

[WIP] Style the visual diff support

Clicking on an annotation card will bring (one of the) highlights
belonging to that annotation into the view in the document.

Restore visual diff to original behaviour.

... by using ES5 sweetness.

Remove the unnecessary per-target hasDiff flag.

Extract the code for calculating the hasDiff/showDiff flags
into a separate method.

Now there are separate test cases for:
 - A single target with no diff
 - A single target with some diff
 - A single target with some diff, which is case only
 - Multiple targets, some with diffs
 - Multiple targets, some with diffs, but only in case

Furthermore, the used sample diff strings actually look like
real diff strings, for better readibility.

Also, removed some useless lines from the code.

(Thx @aron for all the suggestions.)

Fix holes in message threads

This restores the following corner case:

When there is a difference, but it's only about
the case of the characters, don't want to show
the visual diff by default, but we offer the
feature to the user.

I also updated the tests the reflect the specs.