Added block placement handling for several blocks (see #119).

Placement handling for dispensers, droppers, levers, furnaces, and
hoppers. Right-click (toggle) handling for levers.
Use 16-bit (MC 1.8) block types internally.

- Character array is used for unsigned representation.
- Non-air block count is tracked in ChunkSection.
- Retains compatibility with current Anvil format.
- Public API currently remains unchanged.