Initial support for affect scope

Added Enemy and EnemyOnly target type handlers.
Added support for affect scipe "SINGLE".

Fixes #149
Fixes #107

The following skills can only be used in enemies:
Confusion (2)
Lure (51)
Veil (106)

Fixed Shadow Step (821), now cannot be casted without force on unflagged
characters and flags the caster if used on unflagged characters.
On flagged characters do not need force (CTRL).

Reported by: @FinalDestination