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

With only one concurrent build, we can't wait for all the jobs to finish first

Copy-paste-laziness

Update the workspace when changing the target

Because these are peer dependencies, we should be lenient about the required version of React required to use the components.

I didn't use the caret because the x's work and it's obvious what they mean, unlike ^ and ~.

Now they don't have to be built and rebuilt every npm install

Update webpack config and vm usage to match updates in scratch-vm

Also make the toolbox actually get used by scratch-blocks, and update the import of scratch-blocks to use the new shimming method.

Multiple installations of React can cause issues if the package is used just for the components.