Add TickListener component.

TickTask allows registration and calls on each tick.
[BLEEDING] Add simple hover check.
Code duplication for test.
Fix concurrent modification exception for a part.

Only set the hover ticks on teleporting events. On setting back players
in MovingListener.onTick, this will be prevented now. However actions
might still cause trouble, so some non-blocking stuff would be good here
(a removeFroHover set, some other way of keeping track).