* 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.