Tell the player that their game mode was changed

Resolves https://github.com/GlowstoneMC/Glowstone/issues/397
Add Banner Bukkit APIs

(Changes may come is BlockEntityTag stuff is added)
Add Banner MaterialData, and remove base colors from BlockState
Derp, wrong thing.
BannerPattern should not have a base color
Fix non-static method
NullPointerExceptions, not IllegalArgumentException
Add MaterialData for banners to Material
Deprecate magic values
Rename some pattern types to be more descriptive, and fix diagonal cross
Whoops, hanging semicolon