MGEgui resolution selection fix

Fix a crash with the refresh control when opening the resolution selector with a custom window size.

Changed the resolution and refresh selectors to list type.
MGEgui FPS limiter fix

Prevent the FPS limiter from being set to 0, as it causes rendering errors
in Morrowind. Increased max to 144 Hz.
MWSE shader functions

Added functions to control shaders. All script functions work differently to MGE,
not loading shaders or textures at runtime.