Add better support for copied files in Git diffs.

We introduced support for moved files a while back, but copied files
were never properly supported. Copied files with 100% similarity would
flat-out break.

This change introduces support for parsing the copied file info from git
diffs, storing this state in the database, and showing it in the diff
viewer (just like we show moved files). It doesn't require any schema
modifications in the database.

This is the version for 1.7.x. A separate change will be made for 2.0,
since the code has changed enough since than to warrant some slightly
different changes.
Rename the release note *.txt files to *.rst.

In order to provide better compatibility between the release-1.7.x
branches and release-2.0.x/master, this change renames all the *.txt
files in docs/releasenotes/ to *.rst.
Fix an XSS vulnerability in the search results.

Users with full names containing HTML would result in that HTML being
processed by the browser when auto-completing them in the Search field
at the top of any page. This could result in a script in the First or
Last Name fields being executed.

This change fixes the formatItem call to properly escape.

This vulnerability was made public by the reporter both publicly on the
issue tracker (+ mailing list), and on reviews.reviewboard.org. We're
going to cut a new release including this fix quickly as a result.
Release Review Board 1.7.22.
Bump to 1.7.23 dev.
Clean up PyFlakes warnings in 1.7.

In order to keep things clean, I've gone through the PyFlakes warnings
found in 1.7 and fixed them up. These fixes match the fixes done in
2.0, and shouldn't be too painful to merge.
Fix the MySQL docs for max_allowed_packet.

The old docs were not only styled wrong, but were also only showing how
to set the per-session max allowed packet size. This updates the docs to
show where to set this permanently, and to also discuss setting it just
for the session (switching the example to using mysqldump).
Restore the extensions documentation for 1.7.

We moved the extensions docs out of the codebase docs, but this left 1.7
users with no way to get to the new docs. This restores the old docs,
but under the 1.7 manual.
Add "Show SSH Public Key" to new repository form (1.7)

The admin templates are kind of annoying in that if the object doesn't exist
yet, they don't include the object-tools-items block. This meant that the "Show
SSH Public Key" link wasn't shown for the "Add Repository" form.

This change overrides the object-tools block (instead of object-tools-items) to
unconditionally include the <ul>.

Testing done:
Looked at both the "Add Repository" and "Change Repository" forms. Saw that the
SSH key link was present and functional for both.

Fixes bug 3262.

Reviewed at https://reviews.reviewboard.org/r/5626/