UT469d: Fully support gamma, more performance tuning, advanced graphics menu, etc.

This is a large update. The vast majority of what was wrong with the driver is now fixed, the driver is extremely stable, has working HDR support, etc.

Notable changes: The Shaders directory is no longer needed (for UT469). You can safely delete it.

Here's a partial list of things improved upon since the last release (last year):

• Screen-based gamma, instead of per-object gamma (based on the way XOpenGL does gamma)
• Two gamma modes, XOpenGL and DirectX 9 (where there's individual control for each color channel)
• Fix for blurry text when using resolution scaling
• Lots of fixes for using bad texture references
• Selection fixes in both 2D and 3D modes (it's now possible to click and right click the backdrop)
• A config bool to use the DirectX 9 styled flat colors (zone view, bsp cuts, etc.) instead of the lighter default mode
• Screen flashes fixed
• Fixed crashes relating to bad selections
• Better line selection
• Advanced driver options menu when in-game
• Ability for users to use DirectX 10 through DirectX 11.1 GPUs with the driver (by supporting 3 different Pixel and Vertex shader versions)
• Fix for vertex explosion when rendering things like the flag
• More checks for windows versions when trying to request windows 10 exclusive modes
• Shader caching system (not used for this UT release)
• Hard-coded shader support, so the end-user can't edit them nor needs the source shader files (for fair competitive play)
• Removal of the "Per Object" gamma mode, so it's now XOpenGL or DirectX 9 modes only
• Fix Nvidia text rendering going one pixel down and to the right
• Better checks for UV looping when drawing tiles (to fix the texture browser clamping)