Add Plugin installer

[cssjoe]

Add the plugin installer repo to the BoldGrid connect plugin. Make sure that we update the configuration so that it only pulls in public BoldGrid plugins. Since we plan on adding this ticket to the Wordpress Repo, we should make sure that it doesnt install any non WP repo plugins.

After this ticket is done we should consider adding the plugin installer to the other repos.

Make sure that multiple plugin installers can be active at once.