First working scene.

Adds pushbuttons with locking covers.
Adds a Scene component to organize scenes into create + draw.
Adds an Offscreen component to start entities way off screen.
Refactors the main scene heavily.
Updates sprites + sprite sheet SVG.
Fixes lots of bugs.
Adds broken DotMatrix and RotarySwitch components.

Some code exists for DotMatrix, but it's wildly unfinshed.

RotarySwitch is completely empty.