Clean up camera mess

[not-fl3]

• set_default_camera and actual default camera are different. How to test: draw stuff without any set_whatever_camera calls and than add set_default_camera on top. The results should be the same

• make it clear how to create Camera2D with exactly the same params as set_default_camera. Maybe just add the params of that Camera2D to docs of set_default_camera

[profan]

I just ran into this as well, would certainly be nice to clean up eventually :D

[nathanielfernandes]

Just ran into this issue as well, still trying to figure out how to draw correctly to a render target.

[wihrl]

welp, for now i'm using this as a workaround: which, of course, breaks camera.screen_to_world