Point users to Power Pack and support contracts after a site install.

After a user installs a site with 'rb-site install', they're now given
links to Power Pack and to our support contracts page. These are
benefits that we historically haven't done a great job pointing new
users to, so we want them to at least know about them as they're getting
going.

We even make the Power Pack trial process a bit easier by giving users
their install key up-front.

Reviewed at https://reviews.reviewboard.org/r/6020/
Don't strip leading slashes from CVS file paths.

Fetching CVS files requires the filenames to have the leading slashes intact.
This change adds a normalize_diff_filename method to CVSDiffParser which
overrides the default behavior.

Testing done: Ran unit tests.

Fixes bug 3433.

Reviewed at https://reviews.reviewboard.org/r/6029/
Fix spurious logging for FileDiff insert/delete counts.

The logging statements for "overriding" insert and delete counts were
surrounded by conditionals that didn't quite reflect the reality of when things
get overridden. This fixes it so that we don't spam the log files.

Testing done: Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/6032/
Merge branch 'release-2.0.x'