Import features

[HoneyHazard]

• integrated simple shadowmap, parallel split shadowmap, poisson sampling into one branch
• pssm prepare-for-render logic reduced to two passes; depth clamping utilized; extending to shadow casters now used for the frustum test
• shadowmap code reorganization
• code reorganization and more functionality in shader variable use
• sun flare sprite details decouped from the sun flare rendering class
• SSLight functionality split into SSLightBase and SSDirectionalLight