/brz/remove-bazaar

Partial incremental upload implementationm tests pass.

* test_upload.py:
(TestUpload._create_branch): Modify the content of one file.
(TestUpload.test_full_upload): The file content have changed.
(TestUpload.test_incremental_upload): First upload is full, file
content has changed.
(TestUpload.test_invalid_revspec): Add test for revision option.

* __init__.py:
(cmd_upload.run): Separate the working tree from the revision
trees we are interested in.
(cmd_upload.set_uploaded_revid): New method defining the revid for
the uploaded tree,
(cmd_upload.upload_full_tree): Trivial and partial
reimplementation, as a method, of the upload_full_tree function.
(cmd_upload.upload_tree): First partial and trivial implementation
of an incremental tree upload.