Fixed a NullPointerException in PacketHandler when an EnvMapAppearance packet is received during the level loading process.
Fixed third person mode ability being affected by NoClip hack control flag.
Several texture-related fixes.
- Fixed default texture pack being saved as "null".
- Fixed being unable to set sideBlock/edgeBlock/sideLevel if "canServerChangeTextures" is false.
- Fixed textures not getting freed when texture pack is changed.
- Texture pack selection GUI now shows "game broke" message with exception details if default texture failed to load, instead of suppressing errors and leaving the game in an inconsistent state.
Fixed EnvSetMapAppearance not changing map side/edge textures properly. Also fixed a font-related regression in last commit.
Known issue in this commit: changing smoothing and anisotropy settings has no immediate effect. Will fix soon.
Changed most texture name strings (e.g. load("/gui/gui.png")) with constants (e.g. load(Textures.GUI)).
Fixed smoothing and anisotropy settings not taking immediate effect.
Merge pull request #301 from fragmer/master

EnvMapAppearance fix, third person mode no longer limited by -noClip, textures now freed properly.