[WIP] Allow SCMTool Integration through ReviewBoard Extensions

Review Request #6571 — Created Nov. 9, 2014 and discarded — Latest diff uploaded

Information

Review Board
master

Reviewers

There's now a SCMToolHook that extensions can use to register source code management tools. This handles registering, unregistering, and retriving the SCM tools.

TODO:
Write unit tests.
Find where ReviewBoard currently gets its SCMTools.
Integrate the new hook into there.

Ran unit tests.