Implements 1.8 codecs (0x41 up to 0x49) Partially completes #131

Implement ServerDifficulty codec.
Implement CombatEvent codec.
Add 0x43 (Camera).
Packet 0x48 codec added.
Packet 0x44 added (WorldBorder)
Packet 0x45 added. (Title). Some formatting.
Add 0x49 (Entity update NBT). Using varLong now in WorldBorder.

Signed-off-by: William Lebel <lebelwilliam@gmail.com>
Linear interpolation, I don't know the details but its job is to specify how fast the world border is moving.