Add new "World Coordinate" types.

These types provide fixed-point representations of distances, angles,
positions, vectors, and rotations in 3d space.

WAngle (and WRot) represents 360 degrees in 1024 units.
WRange (and WPos, WVec) represents 1 cell in 1024 units.

Distance types in yaml can be written as <cell>c<subcell>, e.g. "4c512" for 4.5 cells.
Add world coordinate helpers to Actor/WorldRenderer/PPos.
Add matrix helpers to Graphics.Util.
Add renderer support for matrix uniforms.
Add renderer support for additional vec* uniforms.
Expose depth buffer to render code.
Expose stencil buffer to render code.

The intention is to provide a layer for tracking shadow
rendering, so a single bit is sufficient for now.
Support Vertex objects with custom z coordinate.
Implement vxl parser.
Implement hva parser.
Store the voxel normals table in a palette.
Add core voxel rendering code.
Allow mods to define voxel sequences.
Add a widget for UI voxels (e.g. colorpicker).
Integrate voxels with world renderer / render traits.