Extract SVN revision number from git log

This patch adds parsing of the output of git log to extract the SVN revision
number tied to each commit. The revision number is part of the git-svn-id
string.
Update GUI to show SVN revision
Add hasSVNRemote to PBGitRepository

This patch adds the ability to query the repo for the presence of any
SVN remotes. This is determined by whether the string "svn-remote" is
present in the repository's .git/config file.
Only load SVN revisions if there's an SVN remote
Hide the SVN rev column if no SVN remote

This patch causes the "Git SVN Revision" table column to be removed
when a repository has no SVN remote.
XIB updates
Merge branch 'refs/heads/master' into issues/169
#169 find revision lines surrounded by whitespace
#169 find revision number even if it's only in the 'subject' line
Add pull request #169 to the change log
Merge branch 'issues/169'