Adding files for the new Quickstart Dashboard plugin.
Adding dashboard plugins and a mechanism for identifying and loading them.

Dashboard plugins will be the main way to add something to the quickstart
dashboard or to perform a task.

By default any class in a file with the same name within the
`dashboard_plugins` directory and that subclass `Dashboard_Plugin` will be
automatically instantiated.
Automatically load plugins in admin.
Add media explorer from Github

Fixes #61
Mirror pre-commit script

Fixes #25
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out of date.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Added basic WP CLI tools for adding repos and scanning them for out of
date repos.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.
Fixing space indentation: replacing with tabs.
Added human-readable message generation, handling diverged branches.

Added a function to generate a human-readable status text for a git repo.

Added detecting and handling for diverged branches.
Only outputting repo status when it is not clean and up to date.