Allow local_site_reverse to take an actual LocalSite.

local_site_reverse was able to take a LocalSite's name, or a request
object, but if you actually had a LocalSite (or None), you'd have to
write your own conditional to extract the name and pass it.

Now, local_site_reverse can take a LocalSite. This saves a database
query, if one is already available, and simplifies calling code.

Reviewed at https://reviews.reviewboard.org/r/6302/
Fix Local Site and validation issues with post-commit hooks.

The post-commit hook support in hosting services had a few issues that
could lead to unintentionally closing the wrong review requests on
other repositories. They also weren't compatible with Local Sites.

The URL for the hook identified the repository, and the URL also
contained the hosting service ID, but we wouldn't use either to properly
validate the repositories. That meant that if a hook was set up to point
to repository 1 on GitHub, and then had a commit referencing a review
request on repository 2 on Bitbucket, things would break.

We now capture the hosting service ID and pass it, the local site name,
and the repository ID to the function that handles closing review
requests. That function will then use that information to narrow down
the list of repositories being processed, in order to avoid operating on
some other review request. The function has also been rewritten to
minimize the number of SQL queries needed.

Local Sites were broken because nothing bothered to check for them. The
URLs were added to the root urlpatterns, and not to
localsite_urlpatterns. There was some code that did something weird with
trying to get a Local Site from a resolved URL, but that didn't really
do anything. Now everything is wired up to allow for hooks on Local
Sites and to restrict operations to review requests on the Local Site.

There's a few other changes here and there to help consistency and to
minimize code. For instance, we had different error responses for
invalid payloads, and they weren't really correct. We just use HTTP 400
now.

Unit tests were added for the three services that support post-commit
hooks. They test hooks with and without Local Sites, and test invalid
repository IDs, Local Site names, and service IDs.

The unit test for testing service registration was also split up into
several tests, since it was testing several things.

Reviewed at https://reviews.reviewboard.org/r/6303/
Merge branch 'release-2.0.x'
Make the Review Dialog use inlineEditors.

Traditionally, the Review Dialog (created either via the "Review" action or
"Edit Review" in the draft review header) had a text box for the body top and
body bottom headers, and a text box for each comment.

This made a lot more sense when the comments were plain text, and the contents
of the text inputs was the same as what the user would see. One thing that
always bothered me about the addition of markdown formatting for comments was
that it was impossible to truly know what you'd get after a review was
published, since we never showed the comments in rendered form. It also meant
that we were potentially creating a huge number of CodeMirror instances, which
made the Review Dialog pretty slow.

This change replaces all the text boxes with rendered text. This makes it more
or less resemble what the user would see after publishing the review. Headers
and footers can be added via the relevant links (either "Add header", "Add
footer", or "Add text" depending on the number of comments), which works a lot
like "Add comment" in the review replies.

The individual comments and other states (whether an issue is open, ship it)
are now all "instant apply". The dialog therefore no longer has "Save" and
"Cancel" buttons, but just a "Close" button. Changes to each individual comment
can still be cancelled.

Testing done:
- Clicked "Review" without a pending draft review. Saw the ship-it checkbox and
  an open/focused inline editor.
- Checked that checking or unchecking "Ship it" would send a request to the
  server, editing the review.
- Clicked "Review" without a pending draft review. Clicked "Ship it" and
  published. Saw a review with "Ship it".
- Edited draft reviews, changing comment text and issue state.
- Added and removed headers and footers, checking that everything was saved
  correctly, and that when the relevant text was empty/null, that the "Add ..."
  links were shown.
- Installed the severity extension and verified that changes to the severity
  fields were saved when clicking "Close" and "Publish".

Reviewed at https://reviews.reviewboard.org/r/6239/