This adds a wpms-stack-helper wp plugin and verifies git settings, for ticket #4 

The WPMS Stack Helper plugin is automatically added to the mu-plugins folder. The plugin will show up on the WP network admin sidebar.

Currently the only thing the plugin does is enable you to let the server do a `git add --all & git commit -m "wpms-stack cron autocommit"` after marking a checkbox on the plugin page. This helps because you then no longer need to login to your server to do the commit manually (for example this is useful after installing a theme or plugin from within the wordpress dashboard).

It works by having WP write a value to a file which is then read by a cron script that runs every minute, if the script finds the value for the autocommit it will commit the files to git and change the value in the file so that on next run it doesn't try commit everything again.

We can enhance this plugin later so that it's capable of more things.