2d drawing improvements

[Xeeynamo]

Fixes various graphics glitches and removes Xe.Drawing dependency for good.

All the game maps were suffering from a bug where transparent elements were not blended correctly with the skybox. This problem has been fixed as the screenshot proves:

There is also another fixed bug, where the game engine was always loading the skybox as SK0, but maps like tt00 have the skybox as SK1

The improved Sequence rendering engine now process loops correctly thanks to my recent discovery. I removed some hard-coded logic to loop certain sequences in the TitleScreen since they were no longer necessary.

Thanks to @kenjiuno discovery regarding the blending mode, I was able to improve the rendering system even more to correctly render complex sequences like the title screen:

Finally, thanks to my recent discovery of sequence being capable to perform UV animations, I was able to replicate this in-game too, and it looks fantastic:

The title screen is still not perfect, as the additive blending mode is brightening the screen too much.
Also, since the game is using MonoGame and the tools Direct3D, the blending mode and UV animations has only been implemented in MonoGame. Therefore those two specific fixes will not be available (yet) in the LayoutEditor tool. The main reason is because I have yet to do some research on how to write a shader for it.