The way that the local repository type was detected overly complicated

and inefficient. We would go through and assemble a complete

RepositoryInfo for each possible repository, potentially doing excess

computation that would just be thrown away. In addition, there were some

situtations where a repository would be operating in a remote-only mode

(for example, using SVN with the --repository-url option) where we

were scanning everything locally before finally using the remote.
This change reworks the local repository detection in RBTools to

work in three phases:

First we ask each tool if it's operating in "remote only" mode. At

   the moment, SVN is the only such tool, but it's easy to imagine other

   server-heavy services gaining this ability.
Second, we scan through each tool to see if it thinks there's an

   active repository. This has been simplified to only fetch the local

   working directory from the tool, rather than the full repository

   info.
Finally, after having chosen a tool, we ask it for the repository

   info structure.

Ran unit tests.
Smoke tested tools that use the repository.