Refactors scenes, adds initial switch display.

Moves the loading scene from game.js to scenes/loading.js. Adds a
switch sprite sheet exported from Inkscape. Adds some of my typical
screen & timer helpers.
Improves ToggleSwitch component.

Makes the toggle switch much bigger. Now uses distance travelled
over the surface of the switch to toggle rather than crossing the
midpoint. Still sluggish on mobile; not enough events are triggered.
Adds a Toggle trigger to ToggleSwitch component.

You can now bind callbacks to respond to the switch changing states.
Fix fade-from-black on every browser resize.

The game is supposed to fade from black when the device is turned
from portrait to landscape (and therefore unpaused). It was fading
from black on every resize event.
Adds more switches, adds pretty lights.

There are now lamps bound to toggle events for each of 8 toggle
switches. Fancy tech demo.

Also adds the source SVG file for the sprites.