Add a branding directive to bring custom branding to sidebar

Fix annotation ID not being passed to moderation banner correctly.

Add missing `vm.` prefix and test. This was missed when testing the PR
because the banner was enabled by modifying the banner's controller
instead of the app state.

* Implement <moderation-banner> component

Implement the UI component for the moderation banner at the top of
annotation cards, following the designs on [1].

[1] https://github.com/hypothesis/product-backlog/issues/183

* Add reducer and actions for managing moderation app state

Add a module which defines the state and actions related to moderation
status of annotations.

* Display moderation banner at the top of annotation cards

The moderation banner is currently only supported on top-level
annotations. It will need to be adjusted and moved to a different
component in order to support replies.

* Support displaying moderation banner above replies.

 * Move the `<moderation-banner>` component to `<annotation-thread>` so
   that it can be displayed for replies as well as annotations.

 * Customize the styling of the banner when the annotation is a reply.

* Add a simple test for display change when moderation banner is used on a reply

* Add additional parameter documentation

* Convert `<moderation-banner>` to a component

As per hypothesis/client#292, all element directives are being converted
to components.

* Add tooltips to moderation banner buttons.

The "Hide" and "Undo" labels for the button were potentially ambiguous.
The final labels are still being discussed but improve the UI by adding
tooltips and changing "Undo" to "Unhide".

* Correct a reference to a button label in tests

The label changed from "Undo" to "Unhide".

https://github.com/hypothesis/product-backlog/issues/181

Say "h" not "the Hypothesis web service"

Move ng components from src/sidebar/directive to src/sidebar/components

Docs adrs tweaks

This makes the dir name match the type of object these modules export.

Convert element directives to components

Add ADR for adopting a component-based architecture for the UI

Query from url

 * Separate the 'Context' section into relevant background information
   and client-specific context.

 * Explicitly state in the 'Decision' section that `angular.component()`
   will be used.

The docs for h now refer to it as just "h" and not "the Hypothesis web
service":

https://github.com/hypothesis/h/pull/4434
https://github.com/hypothesis/h/pull/4435

Update this repo's docs to just say "h" not "Hypothesis web service"
when referring to the web app as opposed to the specific instance of the
web app hosted at hypothes.is.

This ADR provides an explicit write-up of how the UI is structured and
describes some changes we can make to the client to make this structure
more obvious and eliminate inconsistencies.

Components should use `bindings` rather than `scope` to declare inputs
and outputs.

Several directives should be registered as components but will require
refactoring before this is possible.