Branch/persistence listsaves

@davideaster @jessmartin Initiating a pull request and requesting code review for the implementation of the updated persistence listing of saves functionality.

Implementation actually includes a 'modular' entire filesystem based storage implementation (one for nodeJS, one for the ruby server).  Idea was to have a consistent backend module interface so that when we add other storage systems, we can easily swap one for the other (via environment file or similar).