Slaves should pull git repos from the master

- This changes our original design of passing the
project type parameters down to the slaves verbatim.
We now modify them so the url points to the master's
Git repo
Can you fill out the parameter docstrings for the two static methods? Also, for `get_full_repo_directory()` what do you think about adding a few tests demonstrating input and output? (The main reason I ask is because the implementation is kind of difficult to understand what is going on without an example.)