MGFX Improvements

This pull includes two improvements to MGFX processing.

First we now correctly set the texture type for effect parameters.  So you will get the EffectParameterType for Texture1D, Texture3D, TextureCube now.

Second when you define a texture and sampler like so:
```
texture textureMat;

sampler textureSample = sampler_state 
{
    texture = <textureMat>; 
};
```
The name of the effect parameter will now be 'textureMat' and not 'textureSample'.