Add release notes for 2.0 RC 3.

This covers all the fixes and improvements made in 2.0 RC 3. There's a
number of bug fixes, performance improvements, extensibility
improvements, and a couple experimental Web Hook additions in here.

Reviewed at https://reviews.reviewboard.org/r/5758/
Merge branch 'release-2.0.x'
Add input escaping to the bugs section of review

If you create a new review and type a string that should be escaped into the
bugs secion (e.g. <A>), it disappears. Can be fixed by using view.formatText
that escapes input. Note that even though the text that you entered isn't
displayed, if you refresh the review, it's there, and is displayed, as the
template has "|safe" in it. The problem is only visible after immediate value
update.

There are a couple of other fields that might have the same issue, but none of
them (depends on, target groups) are likely to have input that should be
escaped in them.

Testing Done:
Before:
1) Created a new review.
2) Click edit on bug description.
3) Enter "<A>" into the field and press enter.
4) Text disappears.

After:
1) Created a new review.
2) Click edit on bug description.
3) Enter "<A>" into the field and press enter.
4) Text is there, just as expected.

Also tested behaviour with multiple inputs like "<123> <456>".

Bugs closed: 3244

Reviewed at https://reviews.reviewboard.org/r/5774/
Make a small improvement to unicode diffs in 1.7.x

Generally, Review Board 2.0's support for unicode is much, much better than
1.7.x, but this is a small enough change that it's probably worth making. Some
of the filename processing can do operations which will fail if the filenames
an un-decoded utf8, so convert all filenames from diffs to unicode if the
SCMTool didn't already.

Testing done: Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/5784/
Merge branch 'release-1.7.x' into release-2.0.x
Update the 2.0 RC 3 release notes for the Djblets changes.

The release notes were lacking some of the more key changes made to
Djblets. This updates them to include those changes as well.
Release Review Board 2.0 RC 3.
Merge branch 'release-2.0.x'
Fix a typo.
Merge branch 'release-2.0.x'
Make code line numbers work as links

I added two functions to the file, one adds the links to the code line numbers
and the another one removes the link when the code line number isn't hovered.
The link is combined from the file id and the line number, which should be
enough to identify the row, which should be highlighted. The link is removed
from the th element, when user hovers on another row.

Testing Done:
Testing is done on my development server.

Reviewed at https://reviews.reviewboard.org/r/5576/
Jump to and highlight anchors in the diffviewer URL hash.

When people are passing around links to specific lines in the diff viewer, it
helps to be able to see what that link is referring to. This change adds some
highlighting to the given row, and some logic to add in the anchor if it's not
present, since the templates only add anchors for lines that have comments on
them.

Testing Done:
Testing done on my development server locally, works fine there

Reviewed at https://reviews.reviewboard.org/r/5706/
Fix a bug where the body wasn't included in HTTP POSTs

This snuck in during some of the hostingsvcs refactoring. Trivial fix.
Fix extension sandbox tests on master.

The master branch used `extension.id` instead of `extension.metadata['Name']`
for some of the logged messages when extensions threw exceptions. This failed
with the `SandboxExtension` used in the unit tests, since the id is assigned by
`ExtensionManager.load()`, and only for extensions with entry points.

I've manually assigned an extension ID to the `SandboxExtension`, and updated
the other sandbox log messages to be consistent.

Testing done: Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/5791/
Improve use of groups with the GitLab API.

The GitLab API is totally broken with pagination, but if users have a large
number of repositories which are separated into groups, we can do a better job.

This change is based on John Earl's code at /r/5789/, but I've made some
changes to keep things a bit more concise, added a separate error for when the
group name is incorrect, and added and fixed unit tests for everything.

Testing done:
* The original change listed that the groups iteration code was tested against
  a large GitLab installation in both the devserver and production.
* Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/5792/
Switch to ldap.initialize() for AD backend.

The AD backend was still using the deprecated ldap.open() call. This is a
trivial change which switches it over to using ldap.initialize(), which just
takes a URI instead of host/port parameters.
Merge remote-tracking branch 'upstream/master'