Separate settings into different structures

[agustincordes]

The current approach is a bit messy with a single structure housing all the global settings. The plan is to separate them into several structures: Display, Camera, Effects, etc. It will be possible to access these structures via Lua and, for example, create reusable settings:

camera.save(myCameraSettings)
myCameraSettings.fov = 60
camera.load(myCameraSettings)

Depends on issue #91.