* Holding Shift while pressing arrow keys in the editor will scroll by
just 1 pixel per tick to aid in precise debugging with the Zoom In/Out
feature.
* The keybinds used in canvas_editable.go to catch the arrow keys are
updated to use our nice keybind package. As a consequence, the WASD
keys will also scroll the level.
* The "d for Doodads" keybind is renamed "q" so as not to open the
Doodads window whenever scrolling right using the WASD keys.
* Added a Settings window for game options, such as enabling the
horizontal toolbars in Edit Mode. The Settings window also has a
Controls tab showing the gameplay buttons and keyboard shortcuts.
* The Settings window is available as a button on the home screen OR
from the Edit->Settings menu in the EditScene.
* Bugfix: using WASD to move the player character now works better and
is considered by the game to be identical to the arrow key inputs. Boy
now updates his animation based on these keys, and they register as
boolean on/off keys instead of affected by key-repeat.
* Refactor the boolProps: they are all part of usercfg now, and if you
run e.g. "boolProp show-all-doodads true" and then cause the user
settings to save to disk, that boolProp will be permanently enabled
until turned off again.
