This will allow the GUIComponent to have control over the layout

The inline css method gives us nothing that CSS modules can't give us. This puts the project more in line with the way www works, and makes CSS actually readable.

Using class names gives us full control of the modal styles.

Refactor SpriteSelector into "Target Pane" which contains the sprite selector, stage selector, and the buttons for new sprites, costumes and backdrops.

Add a new stage selection component that displays the stage separately from the sprite list.

For now this uses the CSS `filter` property to crudely "highlight" for the active state. This is a temporary solution until we have a real design for the active states.

After doing this, new rules began applying for some reason:

`eol-last` only began taking the 'always' parameter as of 3.6.0, so I needed to update eslint.
`no-unused-var` started warning about process.env after updating the config structure
`comma-dangle` decided to start working, maybe because of the upgrade to eslint?  Autofixed with --fix

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.

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