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 
I find it hard to follow what "data" or "model" is - it seems that these two names are being used almost interchangeably, however with an exception to body of method createGallery which contains line like this ```model: { media: data }```