Interpret world seed as number if possible (fixes #427).
Fetch UUIDs from Mojang if needed (fixes #227, fixes #365).

UUIDs are only fetched if online mode or proxy support is enabled.
Additionally fixes problems when player data files are missing a last
known username.
Fixed or added several broken inventories.

Added GlowInventory#getRawSlots() to handle a protocol special case.
Changed TEContainer to take an inventory rather than an inventory type.
Adds or fixes enchantment tables, anvils, brewing stands, furnaces,
workbenches, dispensers, droppers, and hoppers.
Added ender portal support (see #325).

Adds awardAchievement variant which only awards the achievement if its
parent has already been awarded. Fixes some desyncs with world switching.
Implemented basic damage functionality, including drowning.
Merge branch 'master' into pr-277