* 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

  (How to support multple renames of a single repo? List multiple
  renamedfrom dirs?)

* a way to detect repos in a tree that are not registered, and warn
  about or even auto-register them. (svn externals make this quite
  difficult!)