Doomsday Engine

Model Renderer|Shaders: Multiply vertex color into diffuse texture color

The general-purpose shaders in renderer.pack now multiply aColor into
the color from the diffuse texture map.

IssueID #1995

Renderer|Shaders: "model.skeletal.generic" supports uMapTime, custom UV macro

The generic shader can now be customized with predefined macros.
The PREDEF_TRANSFORM_UV() macro is called before texel lookup.

uMapTime is available for use in the shader, although the default
implementation does not use it for anything.

IssueID #1995

Renderer|Shaders: Added a GLSL include file for reflection cube maps

IssueID #1995

Model Renderer: Added a shared reflection cube map

For now all models will share the same reflection cube map.

IssueID #1995

Renderer|Shaders: Incorporate reflection map to shaders

All generic shaders now support reflection mapping.

IssueID #1995

Model Renderer: Use /home/cubemap.jpg as the reflection cube map

For testing purposes, check for "cubemap.jpg" in the runtime folder
and use it as the reflection cube map.

IssueID #1995