UI improvements specifically for mobile (running the game with the
`-w mobile` or `-w landscape` options) screen sizes.
* Rework the Settings window to be mobile friendly to landscape
oriented screens (`doodle -w landscape`) and migrate Options tab
to magicform.
* The toolbar in the Editor will be a single column of buttons
on small screens, such as `-w mobile` (375x812) portrait mode
smartphone. On larger screens the toolbar shows in two columns
of buttons.
* Fix tooltips not drawing on top.
* Centralize the hard-coded references to specific font filenames
* Add cheat code: `test load screen` to bring a sample loading screen up
for a few seconds. It needs improvement on `-w landscape`
* Add methods `Invulnerable() bool` and `SetInvulnerable(bool)` to the
Actor API accessible in JavaScript (e.g. `Self.SetInvulnerable(true)`)
* The Anvil is invulnerable - when played as, it can crush other mobs by
jumping on them but is not defeated by those mobs at the same time.
* Anvils don't destroy invulnerable mobs, such as other Anvils.
* Bugfix: the Electric Door is considered to be opened from the first
frame of animation when the door begins opening, and remains opened
until the final frame of animation when it is closing.
* New cheat code: `megaton weight` to play as the Anvil by default.
* If the player runs the PlayAsBird cheat they shouldn't be able to win
a high score on a level, so at level startup it detects whether the
DefaultPlayerCharacterDoodad has changed from default on a level that
doesn't use the Start Flag to set a specific doodad - and immediately
marks the session as cheated
