* The game's tick counter was moved from Doodle.ticks to shmem.Tick
where it is more easily available from every corner of the code.
* Fix a bug in the Level Editor where dragging an already-existing actor
from one part of your map to another, would cause it to lose all its
data (especially its UUID), breaking links to other doodads. Now the
existing Actor catches a ride on the drag object to be reinserted
later.
* Animate the Link Line visualizers between actors. They now animate a
blinking color between magenta and grey-ish.
* Load SDL2 fonts from go-bindata storage so we don't have to ship
external font files on disk.
* Dedupe names of doodads so we don't show double on the front-end
(go-bindata bundled doodads + those on local filesystem)
* Use go-bindata for accessing wallpaper images.
* Better flashed messages walking you through the Link Tool.
* Stylize the title screen (MainScene) by rendering a live example level
as the background wallpaper, with mobile doodads in motion.
* Instead of needing to press the "P" and "E" keys to toggle from edit
mode to play mode (and back again), respectively, the UI now draws a
"Play (P)" or "Edit (E)" button on the bottom right corner of the
level canvas. Clicking it will toggle the mode.
* Debug mode: no longer enables the DebugOverlay (F3) by default, but
does now insert the current FPS counter into the window title bar.
* ui.Frame: set a default "mostly transparent" BG color so the frame
background doesn't render as white.
* Add the MenuScene which will house the game's main menus.
* The "New Level" menu is first to be added.
* UI lets you pick Page Type and Wallpaper using radio buttons.
* Page Type: Unbounded, Bounded (default), No Negative Space, Bordered
* Fix bugs in uix.Canvas to fully support all these page types.
