Changed the way the "neutral zone" when rotating is calculated.

This may have caused a problem under certain configurations which
slowed down rotations. Now the neutral zone is calculated as a
percentage of the screen size.
The global speed adjustment is smoother now.
Resolution in fullscreen can be forced accross all systems now.

Also, the default resolution in windowed mode is calculated as two
thirds of the full resolution.
Polished the timers manager.
Removed the "forceFullscreen" setting.