Turret attack strategy

[Glavin001]

• [x] Do not attack enemies within TURRET_MINIMUM_RANGE
• [x] When not under attack
  • [x] move to ideal range from nearest ally archon
  • [x] cannot see ally archon, move towards nearest ally archon

[Glavin001]

Note that the turrets have a minimum attack distance! See http://s3.amazonaws.com/battlecode-releases-2016/releases/javadoc/battlecode/common/GameConstants.html#TURRET_MINIMUM_RANGE

[Glavin001]

So there was already a check for if the turret could attack a location :+1: