Minor style fixes.
Fixed support for 1.8's string-based item ids.
Convert data types during server.properties migration (fixes #392).
Added player visibility API (closes #121).

Players are hidden fron another player's tab list and entity updates.
Also renamed other canSee methods to canSeeChunk and canSeeEntity.
Removed TextWrapper in favor of the client word-wrapping.

Formatting is still a little awkward. When new-style formatting is added
the old-style formatting can be properly converted, fixing any weirdness.
Fixed Player.isOnline() returning true when the player isn't already logged in