* CLI: fix the `doodad convert` command to share the same Palette when
converting each frame (layer) of a doodad so subsequent layers find
the correct color swatches for serialization.
* Scripting: add timers and intervals to Doodad scripts to allow them to
animate themselves or add delayed callbacks. The timers have the same
API as a web browser: setTimeout(), setInterval(), clearTimeout(),
clearInterval().
* Add support for uix.Actor to change its currently rendered layer in
the level. For example a Button Doodad can set its image to Layer 1
(pressed) when touched by the player, and Trapdoors can cycle through
their layers to animate opening and closing.
* Usage from a Doodad script: Self.ShowLayer(1)
* Default Doodads: added scripts for all Buttons, Doors, Keys and the
Trapdoor to run their various animations when touched (in the case of
Keys, destroy themselves when touched, because there is no player
inventory yet)
* Improve the `doodad convert` command to convert a series of input
images into multiple Frames of a Doodad:
`doodad convert frame1.png frame2.png frameN.png output.doodad`
* Add the initial round of dev-asset sprites for the default Doodads:
* Button, Button-TypeB and Sticky Button
* Red, Blue, Green and Yellow Locked Doors and Keys
* Electric Door
* Trapdoor Down
* Add dev-assets/palette.json that defines our default doodad color
palette. Eventually the JSON will be used by the `doodad` tool to give
the layers meaningful names.
* Add the JavaScript system for Doodads to run their scripts in levels,
and wire initial OnCollide() handler support.
* CLI: Add a `doodad install-script` command to the doodad tool.
* Usage: `doodad install-script <index.js> <filename.doodad>`
* Add dev-assets folder for storing source files for the official
default doodads, sprites, levels, etc. and for now add a JavaScript
for the first test doodad.
