Implement Strategist Army unit Rally Points

[krogenth]

With the Strategist play decisions from #43, we can now successfully handle giving orders to our units. For this task we will only consider the defending decision. When defending, we should place our units in the most optimal of locations possible when defending, this is typically:

• on our side of the chokepoint at our base(preferable with Sunken Colonies to help defend)
• on high ground near a chokepoint

For Zerg, our unit range is rather low, so if a chokepoint expands past a Hydralisk's range from the high ground, defending the chokepoint itself should take precedence. Chokepoints can be retrieved from BWEM.