Tweaked sp damage effects to only remove the remaining skill points.
Fixed BattleEnemy revival.

- Made them not stay stuck at idle level.
- Fixed the battle time factor when setting their battle speed.
Added a way to get active status effects intensities on battle actors.
Added support for battle Enemy custom and scriptable AI

I normally shouldn't work on this as I'm currently trying to release something
stable, yet, the player experience is so much better with custom AI that
it's worth the fact to add it now.

This closes #221