This allows the keys to be used for developer shortcuts, but also keeps the "if any key pressed" block working (and hacked key blocks).

This is mostly because it was annoying that Cmd-Opt-J didn't work, but seems like a good thing to have in general.

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.

These were named inconsistently in scratch-vm

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

node relevant at the root, but not in src. Broser relevant in src, but not in root.

null !== undefined

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.

And use instanceOf for the vm prop type