The use of `not is_inside_tree()` before setting the setting class' value
meant that the starting values would always be the default. Moving the
value setting before checking for tree readiness fixes the issue.
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.
