Scratch-vm: Use scratch-storage

[cwillisf]

Expected Behavior

The VM should use the scratch-storage module for loading files. Ideally we should do this in such a way that the storage module could be replaced with a different implementation if necessary.

Actual Behavior

The VM (actually playground.js here) loads project files itself, relies on the renderer to load costumes, etc.

[towerofnix]

Ohhh, more repositories! Modularized code is the best.

Any plan on publishing this repo?

[cwillisf]

@liam4 yep! It needs a little bit of work to make it "official" and then scratch-storage will become public like the rest.