Remove File System API from the core

[impressivewebs]

Not sure if anyone's still working on this, but just FYI - the File System API is no longer a standard, it's been discontinued and is only supported in Chrome. I think it would make sense to just use IndexedDB in all browsers that support it.

[bradwbradw]

Well according to the readme, Chrome doesn't allow blobs in indexedDB, so we'd lose that ability if dropping File System API. I haven't verified this, though.

[bradwbradw]

it would seem that's outdated information, though. according to CanIUse:

Chrome 36 and below did not support Blob objects as indexedDB values.

https://caniuse.com/#feat=indexeddb