Vid 2079 prep gallery JS for outside usage

Setting up a better entry point for VE to consume media galleries. Now, in order to instantiate galleries, simply recreate the logic in controllers/index.js in whatever environment it is needed. 

@inez 
There's a bug in the current implementation of sending lightbox data to galleries, so this option will be removed with https://wikia-inc.atlassian.net/browse/VID-2084. @inez, for VE purposes, you probably want that option set to false anyway.