Improve the title for the Action Hooks page.

The Action Hooks page was called "ActionHook", but the page is actually
about a collection of action hooks. this is a trivial change to rename
it to "Action Hooks".
Fix displaying and publishing drafts for initial review requests.

A review request without a draft that is marked as public=False would be
shown with a draft banner on RB 1.7, but the work on 2.0 broke that.
This was partially due to a change when reorganizing the
review_header.html template, and was further hindered by some missing
logic in the views.

Now, a review request created through the New Review Request page
without a draft will once again have a banner, and the Publish and
Discard buttons will work again.

It also fixes an issue with the error callback for Publish. It turns out
that it didn't have the correct parameters.

Reviewed at https://reviews.reviewboard.org/r/5781/
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/
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/