Fix FPS Limit and VSync Targeting Issues

[HEJOK254]

This PR fixes the following issues:

• The game loading fpsTarget and directly setting it as the Application.targetFrameRate. Since fpsTarget is actually the value of the frame rate limit dropdown, it would result in the game setting the target frame rate to an unplayable value, like 3 or 6 (should be 30 or 60).
• fpsTarget and vSyncRate overwriting each other in their setter functions, resulting in seemingly no saving of those values, and them resetting on each restart/scene change.

Setting both the framerate and vsync targets to 0 is now also allowed, resulting in an unlocked framerate

Note

Please check if everything works properly (mainly on Windows and MacOS) before merging

[HEJOK254]

Related: #68