Adds material definitions for groundcover referencing.
Outpost testbed. contains: multi-layer material terrain, waterplane, vehicle, respawning AI turret, static mesh, particleemitters, timeofday, forest, and groundcover dependencies: #769 for groundcover material definitions, #771 to ensure water doesn't trap the player
Merge branch 'groundcoverMaterials' into terrainblend
Merge branch 'outpost_testbed_clean' into terrainblend