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 think these variables should always be boolean, so something like:
```
options = options || {};
this.lightbox = options.lightbox || false;
this.lazyload = options.lazyload || false;
```
otherwise (in current implementation) you end up with "undefined" being assigned to this.lightbox/lazyload