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.