rbt patch now has full support for patching, outputting, reverting,

and committing single-diff review requests and multi-commit review

requests. When working with Review Board 3.0 or lower, it behaves as it

did before, applying the patch either locally or as a commit based on

the review request's summary and author information.
When working with a multi-commit review request, patches can be applied

sequentially (the default) or squashed, which only makes a difference

when committing. Subsets of commits can also be applied. The ordering of

those commits on the review request are always respected.
Reverting will always apply in the reverse order, ensuring that they're

backed out correctly. When committing the reverted patches, each commit

message will begin with [Reverted].
As part of a modernization effort, all output is now done through

exceptions or logging statements, and the text is localized. While we're

not set up for localization today, the patch code does have a lot of

messages that differ depending on the number of patches, so it made

sense to begin using this here. There are plans to move to a better

approach for command-driven output, which would replace some of this

logging code, but that will be done separately.

Tested this months ago when the code was originally written. This needs

some additional real-world testing, and is being put up for review to

help with that effort.