* workingtree_implementations/test_remove
  - Let getTree check if the files were really created.
  - Add utility method getCommittedTree.
  - Fix test_remove_nonempty_directory to not check for the removal of empty 
    directories.
  - Fix test_dont_remove_directory_with_unknowns to check if we refuse to 
    delete directories containing unknown files or directories.
  - Fix some method names and docstrings as per review
* workingtree.remove
  - Don't automatically remove empty directories.