This is primarily a patch for http://code.google.com/p/reviewboard/issues/detail?id=121 - along with some relevant refactorings.

Changes include
 * Adding function handle_renames which acts like a filter to fix the svn mv/cp issue.
 * Changed convert_absolute_paths to return a list of results like handle_renames for consistency.
 * Made convert_absolute_paths ignore files which where already had an absolute path
 * added a function svn_info which converts the results of 'svn info filename' to a dict and refactored convert_absolute_paths to use it.

I hacked this together because I had a changeset which did do a lot of svn mv/cp. So thats how I tested these changes.

I also checked that it still worked on vanilla changes without svn mv/cp.