Fix issues with Git defaults and SVN file access for Beanstalk.
There were a couple Beanstalk-related issues that were hit in the wild.
The first is that the default repository path for Git repositories was

wrong. People generally didn't notice due to the REPOSITORY= entry in

.reviewboardrc, and since we don't actually use it for anything but

path-based matching.
The second, and more important, is that Subversion flat-out didn't work.

It was using the Beanstalk blob API, which throws an HTTP 500 for

Subversion. I thought this had worked in the past, but it's possible it

regressed. Either way, simple change to make the blob API Git-only.
While at it, I also improved the speed of file checks by not passing any

?contents= to the URL unless we did want contents. It seems the API is

currently treating ?contents=0 the same as ?contents=1.

Tested posting and viewing diffs with Subversion and with Git.
Created a new Git repository and used default path matching in RBTools successfully.
Unit tests pass.