Teach R4 work with R2 shaders.

[Xottab-DUTY]

Along with implementing #281 in commit d38f18d I added support for DX9 shaders in DX11 renderer. (R4)
Time to use this feature and teach R4 to work with R2 shaders. This will require blenders (shading templates) edits mostly. (I think, but not sure)
We should solve this task without modifying original shaders at all. (this will require to write some compatibility layers)

Mostly, this feature is required because we want to support Shadow of Chernobyl (#392) and this game has only DX9 shaders.

[Xottab-DUTY]

Before we can implement this, we should accomplish #526