Bugfix: hold the attack option calculator to focus bounds

 - Fix a bug where attacks could use more focus than allocated thus
   producing invalid attack options.
 - Implement a new strategy, "_focus_capped_aggro", which factors
   focus usage into attack plan rankings in an attempt to achieve
   greater efficiency.
 - Add a 'focus' key to each attack step as a means of tracking focus
   usage.
 - Implement a reduced form comparison between attack plan lists which
   allows for duplicate and reorder plans to be discarded out of hand.