Adds support for sound effects in Doodle and configures some for various
doodads to start out with:
* Buttons and Switches: "Clicked down" and "clicked up" sounds.
* Colored Doors: an "unlocked" sound and a "door opened" sound.
* Electric Door: sci-fi sounds when opening and closing.
* Keys: sound effect for collecting keys.
JavaScript API for Doodads adds a global function `Sound.Play(filename)`
to play sounds. All sounds in the `rtp/sfx/` folder are pre-loaded on
startup for efficient use in the app. Otherwise sounds are lazy-loaded
on first playback.
* Tightens up the surface area of API methods available to the
JavaScript VMs for doodads. Variables and functions are carefully
passed in one-by-one so the doodad script can only access intended
functions and not snoop on undocumented APIs.
* Wrote tons of user documentation for Doodad Scripts: documented the
full surface area of the exposed JavaScript API now that the surface
area is known and limited.
* Early WIP code for the Campaign JSON
