Major commit - added ground depth, scattering function + assets, shadows and rendering improvements

Added generator assets from scattering - trees, bushes, grass; textures
added; Scattering rewrite - nothing scatters near trees; only grass
scatters near border; modified scatter order from biggest to smallest,
also moved riggid bodies last; Pebbles now put to sleep after spawning;
project quality asset updated to render shadows; Player shader updated
to transparent with shadows; Added two 2sided diffuse shaders that are
not used;
Merge branch 'mtra_interactables' of https://github.com/Oragada/WeShouldExplore into mtra_interactables

Conflicts:
	UnityProject/Assets/Models/Materials/player.mat
	UnityProject/Assets/Tree_Textures.meta