Alternate render targets and dynamic textures

[axefrog]

Currently the engine can only render to a window. Need to allow other targets in order to facilitate user interface development, compositing, etc.

Primary cases:

• Generate a texture using C# code and use it as a texture resource
• Make GPU draw calls to a texture render target and then use that as a texture resource
• Support 1D, 2D, and 3D textures, as well as texture cubes and texture arrays
• Create and update texture resources by drawing directly to texture memory on the CPU side
• Render to a texture resource (render target) using GPU draw calls
• Merge multiple dynamic texture resources into a final composite scene, with alpha blending

[axefrog]

http://www.tecton69.com/2015/01/15/Dynamically-Change-Texture-in-DirectX-11/