Darkage slabs/stairs cannot be crafted anymore

[davisonio]

Probably due to a moreblocks update. Causes some stuff in bug

What needs to be done

• Completety redo the darkage stairs and slab registering using the official API
• Create aliases for all darkage blocks in a suitable place, aliases.lua

https://github.com/Calinou/moreblocks/blob/master/stairsplus/API.md