Fixed not being able to place blocks inside snow.
Completely obliterate rogue threads on exit (fixes #179).

The shutdown monitor thread is now more thorough about killing the threads
it finds, and will still terminate even if a thread could not be killed.
Added 1.8 crafing recipes (see #314).

4x red sand -> 1x red sandstone
4x red sandstone -> 4x smooth red sandstone
2x red sandstone slab -> 1x chiseled red sandstone
2x stone bricks slab -> 1x chiseled stone bricks
2x cobblestone, 2x quartz -> 2x diorite
4x diorite -> 4x polished diorite
4x granite -> 4x polished granite
4x andesite -> 4x polished andesite
2x dirt, 2x gravel -> 4x coarse dirt
3x red sandstone -> 6x red sandstone slab
bunch of things -> rabbit stew
4x rabbit hide -> 1x leather
4x oak plank, 2x stick -> 3x oak fence
fences: spruce, birch, jungle, acacia, dark oak
2x oak plank, 4x stick -> 1x oak fence gate
fence gates: spruce, birch, jungle, acacia, dark oak
doors: oak, spruce, birch, jungle, acacia, dark oak
6x iron ingot -> 3x iron door
4x iron ingot -> 1x iron trap door
7x stick, 1x stone slab -> 1x armor stand
6x red sandstone -> 4x red sandstone stairs
1x stone brick, 1x vine -> 1x mossy stone brick
1x cobblestone, 1x vine -> 1x mossy cobblestone
1x diorite, 1x quartz -> 1x granite
1x diorite, 1x cobblestone -> 1x andesite
9x slime ball -> 1x slime block
1x slime block -> 9x slime ball
furnace: stone brick -> cracked stone brick
4x prismarine shard -> prismarine
9x prismarine shard -> prismarine brick
8x prismarine shard, 1x ink sac -> dark prismarine
5x prismarine crystals, 4x prismarine shard -> 1x sea lantern
furnace: rabbit -> cooked rabbit