Allow superusers to access private repositories.

Trivial patch to allow superusers access to all repositories.

Fixes bug 3118.
Fix error reporting for API requests in the commits view and elsewhere.

The commits view wasn't showing any error responses when failing to
create a review request. It now displays an alert and clears the
spinner.

While working to fix this, I realized our error handling wasn't correct.
We weren't taking in the correct parameters in syncOptions.error that
RB.apiCall passes, and we weren't passing the arguments that Backbone's
wrapError expects. This now wires everything up so that errors coming
from the server will be properly represented in error handlers.
Fix JavaScript unit test regressions with file attachment deletion.

The recent change to fix deleting file attachments broke the unit tests,
which were never receiving a response back from the new ensureCreated
call on the draft. We now spy on that and fake a success.
Hide the Repository field if not using a repository.

The new field code regressed the visibility of the Repository field when
no repository was found. We now hide it if there isn't a repository on
that review request.
Speed up tests by reducing the initialization work.

The initialize call performs a lot of operations, the majority of which
aren't needed for unit tests. By cutting off this work, we save a few
seconds in total across the test run. This doesn't appear to have any
negative impact on unit tests.
Improve line number reference URLs for the text review UI.

For the text review UI, you can reference a line number by
appending #source/line123 to the URL. This improves it a bit by allowing
just #line123.

Since Backbone.Router isn't very smart when it comes to
pattern-matching, we have no way of specifying a mode just for line
numbers. The greediest entry seems to win, and that'd be the :viewMode
one. So, we need to transform in the router handler.
rb-site: Deploy correct Apache 2.4 authorization

Apache 2.4 uses a different authorization config than 2.2. This change adds
some smarts to rb-site to detect when using Apache 2.4 and use "Require all
granted" instead of "Allow from all".

Testing Done:
Applied the patch and deployed it on a system with Apache 2.4.2. It properly
detected the version and put "Require all granted" into the apache-wsgi.conf

Bugs closed: 3210

Reviewed at https://reviews.reviewboard.org/r/5338/
Merge branch 'release-1.7.x'