Create AI handling for ranged units

[CameronJung]

The AI will need to understand the following to use artillery properly:

• [x] AI is able to use artillery to attack
• [x] AI is able to move artillery units
• [x] AI considers artillery more valuable than other vehicle units
• [x] AI understands that infantry are a threat to its artillery
• [x] AI understands that it can kill enemy artillery with its infantry
• [x] AI avoids placing its units within range of the player's artillery
• [x] AI gives less value to moving artillery closer to the player's base

[CameronJung]

I'm scaling back the scope of this issue a little bit due to time constraints. Their won't be "special cases" like I previously envisioned, such as the AI trying to place the artillery in strategic locations. I will just settle for the current logic applied to the new unit.

[CameronJung]

The method "Perform Tactical Analysis" in the selection manager should be rewritten to use the new hex affect system

• [x] Tactical analysis is performed using the hexaffect system