GRAPHICS: Clean up the MaterialManager a bit
GRAPHICS: Move the material list into Renderable

No need for the hacky collectMaterials() method anymore.
Instead, a list of materials is held by the Renderable,
and a makeDynamic() method converts all materials of a
Renderable into dynamic materials.
JANITORIAL: Remove unused variables
GRAPHICS: Add Renderable::forceTransparent()
GRAPHICS: Add Model::forceTransparent()
NWN: Add ModelWidget::forceTransparent()
NWN: Hardcode the expansion logos and the shadow overlay transparent
KOTOR TESTCASE