More stairs, more slabs

This modification adds more types of slabs and stairs to Minecraft. Now in the beta version it adds half-blocks and stairs for concrete and its other types. Each half-block or staircase has its own recipe for crafting, which is relevant to Minecraft recipes.
 This means that you get four steps from crafting stairs and six half-blocks from crafting a half-block. Please note that the modification is in BETA mode and is therefore not 100% complete.