Menu Text

The buttons on both the Main Menu and the CombatMap menu bar now have
text labels.
Turn System Proof of Concept

Implemented functionality for the End Turn button on the CombatMap menu
bar.
The End Turn button ends the turn of all currently active Agents and
begins next turn. When all Agents have ended their turn in a round, a
new round begins.
Added a bounds check when updating the strings that display the cursor
position to eliminate a fatal exception with unsafe values.