Better Slabs Mod

- added survival mode support
-- you can now craft all slabs(except 3 types from usually unobtainable blocks)
-- you can craft slabs back into full blocks by putting two pieces of slabs on the crafting table*
-- all block drops are equal to slabs' full blocks meaning silk touch applies to glass-like slabs
- added a few 'basic' blocks
-- bookshelf, brick, mossy cobblestone, obsidian, netherrack, clay, snow, stone brick (including variants), nether brick and end stone slabs
- fixed a few bugs and glitches
-- fixed spruce planks slab looking like vertical spruce log slab
-- fixed having this mod's slabs in your hands making glitches on the screen where the hunger bar is
-- fixed glass slab being considered a full block by the game engine

Note:
Crafting slabs is very strict! To craft them, you have to fill the FIRST ROW with a full block to make slabs from this mod. Otherwise, it won't work.