SDL_Window Double Window Fix Start

I figured out why there were two windows being drawn in Windowed Mode -
the if statements in the SetWindowedMode and SetFullscreenMode methods
of the Storm3D class need some work.
Window Work

Added a CheckWindowCreated function to comply with SDL2 standards.
Cleaned up the SetWindowedMode function by removing most of the old code
from it.
Added appropriate comments to the new functions to comply with the rest
of the code.
Destroy SDL2

To comply with SDL2 standards, I added SDL_DestroyWindow right before
deleting s3d.
More Fullscreen Work

To comply with SDL2 standards, I removed all of the preset modes from the
SetFullScreenMode function, added two iterators to get both the
CurrentDisplay and how many total DisplayModes are available, and, if
the current width and height are greater than the CurrentDisplay, set the current width and height to that of the CurrentDisplay.
Merge branch 'Fullscreen-Work' into linux