[PATCH 0 of 5] Feature: Add branchmap to convert extension

[Michael J. Pedersen]

Please disregard the feature from last night. It turns out it was broken.

This updated patchbomb adds the feature correctly, adds the automated
tests, and passes all existing tests.

This adds --branchmap to the convert extension, allowing a user to rename
branches during the conversion process. This allows for merging of trunks
from divergent repositories as branches.

This is most handy when trying to convert a badly mismanaged SVN repository
with branches in multiple locations. This allows you to split each branch
into its own Mercurial repository, and then use convert to merge them back
in at the proper location using splicemap and branchmap combined.

And this finally allows me to finish the conversion I've been working on
for a while now.