* To the MenuScene add the "Load Drawing" window UI.
* Displays the user's Levels and Doodads using rows of buttons, 4
buttons per row. Clicking the button loads the EditorScene with that
filename.
* Free Version does not display the Doodads label or button on this
menu screen.
* 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.
