Beginning of Target Selector work

Began work on a target selector object for battle. When finished, this
can be used for items, spells, attacks, etc. Any battle action. It still
has a long ways to go, functionality wise, but the foundational code has
been laid.

KNOWN BUGS:
* Backing out from the target selection to 2 menus previous does not
correctly change focus
* Sometimes the arrow fails to draw when selecting a target