* more revision control systems

* support for tracking repo renames

  It should be possible to tell mr that there used to be a repo at
  src/foo/bar, and it's been moved to src/bar. mr would then detect if the
  move needs to be done, and handle it. This is mostly useful when mrconfig
  files are shared accross several systems.

  [src/bar]
  renamedfrom = src/foo/bar

  (Support multple renames of a single repo?)