Revert "adds obsidian"

This reverts commit bb9a25381e619e116a0d6b18b36353d37cf2011b.

Conflicts:
	mods/default/init.lua
	mods/default/textures/Thumbs.db

	modified:   mods/default/init.lua
	deleted:    mods/default/textures/default_obsidian_glass.png
	deleted:    mods/default/textures/default_obsidian_rock.png
	deleted:    mods/default/textures/default_obsidian_shard.png