Rename Device->GlBackEnd and DeviceTask->ApiBackEnd to reduce confusion
Rename device::Server->device::Device to reduce confusion
Add some documentation
Remove uninhabited types and simplify type signatures
Merge pull request #81 from bjz/device-type-renames

Type renames and simplifications
Added capabilities for vertex array buffer and uniform blocks

Made the gl device recognize both capabilities
Merge pull request #78 from Kimundi/compat_caps

Added capability detection for vertex arrays and uniform blocks
Added a basic Rast module to the generic device and GL backend.
Improved the primitive state, fully implemented on GL backend
Depth test implemented in the GL back-end
Moved DrawState into the render module and exposed to the user.
Added cull & depth helpers for DrawState
Added Blend state types.
Blend mode setup implemented on the GL back-end
Implemented basic blend presets.
Fixed face culling, enabling by deafult now.