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.
Fix one more unicode issue in diffs.

Most of our unicode issues have been fixed, but there was one lingering in the
interdiff code. Trivial fix.

Fixes bug 3291.
Fix some bugs with post-commit creation with subvertpy.

The subvertpy backend for post-commit review request creation had a bug where
it was passing in a string for the base revision to the diff method. This is
fixed easily enough by ensuring that revisions are ints.

While I was doing this, I found that trying to create post-commit review
requests for commits which are in a protected part of the repository (such as
security fixes in the ASF repo) would show the user a dialog that says "HTTP
Error 500". I've converted exceptions in the diff method to SCMError, which
will at least log and return something slightly less ugly to the user.

Testing done:
Created some post-commit review requests for commits in the WordPress and ASF
repositories.

Reviewed at https://reviews.reviewboard.org/r/5623/
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/
Add "Show SSH Public Key" to new repository form (2.0)

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/5627/
Update Review Board for the DataGrid state changes.

Datagrids now have a separation of state and definition. This requires
some changes in Column subclasses to make use of the new state
parameters.

As part of the new fixes, we're also able to fix sorting of the review
request ID column, which broke in RC 1.
Merge branch 'release-1.7.x' into release-2.0.x
Merge remote-tracking branch 'origin/release-2.0.x' into release-2.0.x