Split up --repository-url and REPOSITORY into new options/settings.
--repository-url and REPOSITORY had both previously allowed either a

path to be specified, or a repository name. We'd try for the name when

looking up a repository, but would try for the path in different ways

within the SCMClients. In the case of Subversion, this broke pretty

badly when using a repository name.
Now --repository-url has been split into --repository-url and

--repository, while REPOSITORY has been split into REPOSITORY_URL and

REPOSITORY.
The URL-based ones work as they previously did, while the non-URL ones

are used for repository name-based lookups only.
This will require that people update their scripts or .reviewboardrc

files if passing the old values for the settings, but in the long-run,

it should avoid a lot of problems.

Unit tests pass.
Tested with Subversion (which was the one that broke the most):

Posting a valid URL with --repository-url worked.
Posting a valid name with --repository-name worked and did not break the svn info command.
The above with their equivalent .reviewboardrc options worked.
Tested the above with invalid values and saw that it failed, as it should.
Switched repositories using svn switch to prevent path-based matching and re-did the above tests.