Move world generator warning to CraftBukkit. Fixes BUKKIT-2565
Updated version to 1.5.2-R0.1 in pom.xml for BETA.
Updated version to 1.5.2-R0.2-SNAPSHOT for development towards next release.
Implement command tab completion in the console. Adds BUKKIT-4168

To accomplish this 2 changes to Bukkit were required:
- the player check in Command.tabComplete() had to be removed
- the SimpleCommandMap prepends the / only for players
fixed a CCE in Command.tabComplete() introduced in the last commit