Improve javadoc in 26 files.

Addresses:
BUKKIT-1643, BUKKIT-1868, BUKKIT-1846, BUKKIT-2632, BUKKIT-3196,
BUKKIT-3187, BUKKIT-3198, BUKKIT-3200, BUKKIT-3201 and BUKKIT-3417.
Don't try listing something that may not exist. Fixes BUKKIT-3471

The player name may not be provided, in which case the command will
fail hard.
Only use TravelAgent if supplied; Addresses BUKKIT-3466

If there is no TravelAgent assigned, it can not be used.
Spigot POM Changes
Measure the duration of the entire timings run.
Add CustomTimingsHandler for adding new CraftBukkit custom timings
Make the plugin class loader thread safe
Merge branch 'master' of git://github.com/EcoCityCraft/Spigot-API

Conflicts:
	src/main/java/org/bukkit/command/defaults/ClearCommand.java
	src/main/java/org/bukkit/command/defaults/TeleportCommand.java
	src/main/java/org/bukkit/command/defaults/TimingsCommand.java
	src/main/java/org/bukkit/command/defaults/WhitelistCommand.java