Only make aliases automatically for stairs and slabs from MTG stairs mod. Let other mods worry about aliasing themselves. Fixes minetest-mods/moreblocks#45
* Make wool sawable
Based on my simple research https://github.com/minetest-mods/moreblocks/issues/71 enabling wool should not cause major slowdowns.
Code pasted from gloopblocks
* List wool as optional dependancy
* Added check for wool dependancy
* Make life easier for translators
