Preparation for Proof of Concept Turn System

Added counter for the current number of Agents.
Added arrays for an initial Proof of Concept for the Turn and Initiative
systems.
Added 2 additional Agents during the CombatMap initialization.
The sizeof() function is no longer used when iterating.
Fixed a bug with the rendering of overlapped Agents.
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.
Player Initiative Proof of Concept

Added Proof of Concept implementation of Player-by-Player Initiative and
Turn system.
- Multiple Agents may have simultaneous turns if they are owned by the
same player and have higher initiative than any other player's Agents
that have not yet had a turn.

Added additional Agents to test and better illustrate Proof of Concept
implementation.
Added additional sprites for Agents to better illustrate Proof of
Concept implementation.
Agents now keep track of an integer to identify which sprite should be
rendered when rendering an agent.