[Abilities] Renamed specials to abilities
[Abilities] Renamed set to category

On the one hand setSetName and setName could sound misleading in the qt
client patch i plan. On the otherhand i never really liked the name
"set". I think category is more general and obvious.
[Abilities] Added network message for removed ability

This prevents really nasty code clientside
[Abilities] Turned special 1 into a point target for easier testing
[Abilities] Only send status for actually changed abilities

Previously *every* ability was spammed over the network regardless
whether it was changed or not.