Used `var variable := 0.0` as discussed in the Godot issue, instead of
`var variable: = 0.0`.
Mostly these are minor/cosmetic changes, but I've also reorganized the
folder structure (naming of folders) to reflect our guidelines, plus
made some minor changes to the demo codes. Still work in progress.
Since we don't want to come up with a GUI maintenance system and
instead focus on the steering behaviors, all relevant variables have
been moved as exported in the main demo script for each toy.
