Multiple moves branch

The multiple moves branch is functionally complete. There may be a few
more tweaks, but the client API and command-line client changes have
been finalized.

The major features are:
- Ability to do multiple wc->wc, wc->repo, repo->wc, and repo->repo
  copies with one call into the client API (and hence one svn cp
  command.)
- Ability to do multiple wc->wc and repo->repo moves with one call to
  the client API.
- Rev'ing the client copy and move APIs to accommodate this new
  behavior.

Most of the work has been in libsvn_client, with some minor changes
to the command-line client.

There haven't been very many comments as I've committed to the branch,
which probably means one of two things: people haven't had a chance to
review, or I write infallible code. Seeing as how the latter is highly
unlikely, I'd like to request that folks review the branch diff.
Feedback is heartily solicited!

Thanks for the extra eyes, and I'm excited to see this merged into trunk.

-Hyrum