Added the EnemyManager class.
Added declarations to the EnemyManager class.
Added Initialize() method to the EnemyManager class.
Added AddEnemy() method to the EnemyManager class.
Add Update() method to the EnemyManager class.
Added Draw() method to the EnemyManager class.
Changed the Update() of the ComputerTerminal, to allow it to spawn enemies.
Added EnemyManager.Initialize() to the LoadContent() method.
Added the EnemyManagers Draw() and Update() methods to the respective methods in the TwinStickAction class.