Adding RepoMonitor plugin and CLI tools.

Added the `RepoMonitor` plugin that is responsible for monitoring all git
and svn repos in quickstart and notifying the user when the repository is
out of date.

Added the basic repo monitoring and scanning functionality. SVN is not yet
functional. Currently working on parsing as much information as possible
from the git output.

Added basic WP CLI tools for adding repos and scanning them for out of
date repos. Does not yet support updating repos.