Add support for -X to the Bazaar SCM Client.

Review Request #6349 — Created Sept. 20, 2014 and submitted — Latest diff uploaded




Bazaar now supports excluding files from diffs and posts via
rbtools.utils.diffs.filter_diff, which looks through the
output of bzr diff for lines indicating the start of a file's
diff. If the file specified matches any pattern, that file's
diff is excluded from the resulting diff or post.

Add a test for checking the result of the BazaarClient's diff
with file exclusion.

Unit tests pass.

Ran rbt dff -X .. in a Bazaar repository and got the specified file was
not included.