Initial rough sprite/costume/backdrop libraries

# Conflicts:
#	package.json
#	src/containers/gui.js

Makes local deployment easier

So that you can adjust them without redefining the entire GUI.
Also allow adjusting props passed to GUIComponent.

So that it's easier to use these standalone.

`npm update` does what we want and is less hacky than removing the packages entirely first.  Specify latest as the version so we always get the latest version even though I erroneously installed scratch-blocks@0.1.0.

And use instanceOf for the vm prop type

Move behavior-related components to "containers", leave presentation components in "components".

Confine the logic for adding/removing event listeners between the VM and the components to the relevant components.  While this tightens the coupling between the component and the environment, it makes using the individual components more self-contained.

Use fewer refs, these had weird behavior that caused the order of components to matter.
Attach events eagerly, as soon as the necessary objects are available.
Make VMManager an actual class instantiated with a VM so we don't have to pass it to every method.
Use bindAll everywhere for convenience.

Attach flyout listeners to GUI workspace

Use default toolbox from scratch-blocks

Once another project uses this package, these should become peerDependencies.  Until then install automatically.

While doing so:
- Use ProjectLoader for loading projects
- Stop using loadEmptyProject and supply empty project data
- Move project loading to App, GUI now receives data (as a string - the vm should receive an object eventually)
- Add logging