Add better help text to the repository form's Path field.

Our help text for the Path field was a big ol' mess of information for a
variety of SCMTools, and certainly didn't scale or look readable.

We now allow SCMTools to provide their own help text for any fields they
choose (though right now, it's only used for Path). When switching tools
on the repository form, the help text for all affected fields will
change.

The existing help text has been split up into the various SCMTools we
previously documented, and cleaned up a bit.
Choose a better default for the hosting account on the repository form.

When switching hosting services on the repository form, the Account
dropdown would default to "<Link a new account>", unless there was
already a matching account selected before. This is not a good default
when there are actual, valid accounts previously linked.

Now we choose the 1st real account as the default, unless we find a
previously selected account in the list, in which case that'll be the
default.
Add API support for creating a review request with no repository.

Our API wasn't allowing the creation of review requests without a
repository. This should be allowed, as the web UI allows it, and not all
review requests going forward will have anything to do with diffs.

The 'repository' parameter is now optional. Documentation was updated to
explain the new usage of this parameter.
Fix a memory leak with the new in-database SVN cert storage.

The new SVN cert support introduced a memory leak due to a circular
dependency.

The client was holding on to a reference to the function on SVNTool,
while SVNTool was holding on to the client, preventing either from being
cleaned up.

An attempt was made at inlining the function, but as that accessed data
bound to the class, the circular dependency remained.

This appears to be an issue specifically with PySVN, as an independent
repro case could be devised for pysvn.Client's callbacks, but not those
from a mock object.

The callback is now defined as a classmethod and the only attribute it
needs, a repository, is set up as a weakptr which is then accessed by a
lambda calling the callback. This prevents the repository and SVNTool
from remaining around indefinitely.
Fix the style for the comment save bubble in the diff viewer.

A CSS rule was introduced for the floating collapse div in the diff
viewer that broke the style for the comment save bubble. The border of
the bubble was no longer covering all the text, which looked very
broken.

The div for the collapse button has been given a class and the offending
rule has been updated to specifically make use of that class.
Dynamically generate the webapi resource tree docs.

The webapi resource tree docs were hand-generated, and out of date.
This adds a new ReST directive to spit out a resource tree based on
what's in the webapi resources list.
Stop including flup.

flup is needed for fastcgi, but their site has been down for a while
now, and we recommend wsgi, so stop bundling it with Review Board.
Add resource docs for review group user lists.
Document the missing webapi errors.
Fix a typo in the Group Already Exists API error.

A space was missing between "already" and "exists."
Fix the examples for resource payloads in the webapi docs.

We were showing examples for every allowed mimetype for a resource, but
this meant that we ended up showing both the generic (application/json)
and specific (application/vnd.reviewboard.org.<resource>+json)
mimetypes. To make it worse, we didn't apply proper formatting to the
latter.

We now filter out the generic mimetypes that we know we'll have
specifics for, and make sure to be smart about when to apply formatting
to mimetypes.
Add the new resources to the index.