Fix slave skills

[Henrybk]

Fixes #3913

Each actor now holds their own skill list.

Possible problem is that I don't know actually how skills are handled in the server, if they are coded as a character skill then their use must remain in AI::Corelogic, if however slaves are their own separate entity with cooldowns of their own then it would probably be wise to move their skill usage to their AI.

EDIT:
It does seem char and slave are completely independent, I'll move the skill use logic to their AI

EDIT2:
Done, just gotta test it

Edit 3:

Video showing it working:
Youtube

[Henrybk]

Tested both mercenary and homunculus for about 4 hours each, using both basic attacks and attack skills, got no errors during that time, I believe this is safe for merge.

During testing however I noticed that in new clients the server not always sends the proper packets for homunculus info, which can lead to crashes, in my testing that happens only when homunculus is dead and you interact with another slave however.
I will try to fix that also but it is beyond the scope of this pull request.

Also, in the future I will move slave selfskills to their AI in another PR.

[alisonrag]

LGTM