Clean Up Scripts

[Jowan-Spooner]

Why: Because I would like the code-base of 2.0 to be relatively clean and well-done before release. This is not necessary before the beta tho.

Big Cleanup necesaary

• [x] TimelineEditor.gd
• [ ] EventNode.gd

Both have been copied from 1.x and are thus pretty unorganized and likely contain unnecessary code.

Cleanup for all scripts

• [x] Event scripts
• [x] Resource scripts
• [x] Subsystem scripts
• [x] Display Node scripts
• [x] Editor scene scripts

What I suggest:

• rename methods and properties to be as self-explanatory as possible
• make use of the gdscript styling guide
• remove unnecessary code
• add an explanation at the top of each script on what it does
• sort/organize methods into
  • main methods (those that are the main purpose of the script)
  • helper methods
  • ui methods
• make clear what methods are for internal and external access (for example by consistently starting internal methods with _ or sorting them into specific sections)