!!! Added PBR Shader !!! Re-implemented video support with WebM * Ported the Core shader, prop_coreball and prop_scalable from HL2 * Added cvars to set the view height and crouch height * Added a Keep Player Position spawnflag to prop_vehicle_choreo_generic * Added materials for weapon_cubemap

* Fixed 3D viewport camera FOV config not being saved in Hammer * Fixed portalgun worldmodel jitter * Fixed prop_portal particles not rendering after replacement