Unify the LineType and PrimitiveType for rendering.
Cast away these warnings.
Allow CityOnPlanet to use SGM files.
Remove all of the base class definitions for virtual methods.
Utility method for the VertexBuffer classes, copies a VertexArray into a VertexBuffer to aid in porting code across.
Add new Drawable types and convert existing ones from VertexArray to VertexBuffer where applicable.
Remove Drawable base class.
Merge pull request #3187 from fluffyfreak/more-drawable

More drawable classes, minor fixes