Move video store (and maybe more) to IndexedDB

[daviddeutsch]

This might also fix #79. Candidates for inclusion:

https://github.com/webcss/angular-indexedDB

https://github.com/OpenLMIS/indexed-db-angular-service

Second one seems a little slim, not sure why. Might be missing maturity or a higher level of cleverness compared to the first.

Further reference:

https://developer.mozilla.org/en-US/docs/IndexedDB

In general, this should speed up yt-sanegrid a LOT. Maybe I'll end up using localStorage just for fallback, although for stuff like settings, it might be faster in general.

[g-rocket]

You might want to also use axemclion / IndexedDBShim to support more browsers