Improved nape classes documentation

- Some of the documentation in there seemed outdated, `createPhysObjects()` for example which is mentioned there, doesn't exist (anymore?). Heavily improved docs in general.

- Added docs to all the functions and vars that didn't have any except for `FlxPhysSprite._radsFactor` because I'm not entirely sure what it does.

- Added return type `Void` to all functions that didn't have one.

- Truncated and organized imports.

- Capitalized all function params and added docs for them. Where it wasn't possible due to the capital version of the param name being a class in Nape, I added an underscore:
`?type` -> `?_Type`

- Also removed all uses of `this`.