Add debug overlays to look at layer properties

[DCNick3]

I really like the impl by kira audio, would copy some ideas from there. Also, they are apparently called "tweens", for "in beTWEEN"

Wanna:

• [ ] Some debug overlays for layers ¿& other? tweens
• [x] Warnings on unimplemented layer properties

[DCNick3]

Refactoring mostly done, though missing a lot of weird features available in the engine (the assortment of flags). Debug overlays will come later ig