Update the trigger command

Simple commit, just updating the Trigger command to the 0.9 standards
This also fixes a bug in which the 'cooldown:' argument didn't work at
all. (NPE on usage, due to improper argument handling)
Remove empty CommandExecutor error message

in some situations, this message is empty... don't show it if so.
(EX: not enough arguments exception uses an empty message)
Merge pull request #536 from mcmonkey4eva/master

Yet Another Pull Request