Allow the WalkCommand to take a list of NPCs

This will make the entire list of NPCs walk towards the same target.
Specify a radius: to cause the NPC group to *flock* to the target,
meaning they will all go together while carefully not running into /
through each other, and end up no further spread out than the given
radius.
Uses a brand new Citizens API feature, be sure to update Citizens before
using!
Clean kick message for login event cancelling

- determine "KICKED for potatoes"
Will now show "for potatoes" instead of "KICKED for potatoes"
Also add meta for that style
Default the break command to the linked NPC

NPC's can be forced to break blocks... players, not so much.
Merge pull request #610 from mcmonkey4eva/master

Pull request, with features!