Improve tower rotation

[sdiaz7]

Definition of Done

• Dependency on #162
• Turrets rotate over time instead of instantly
• Idle rotation when no target is available

[sdiaz7]

Try this if you want towers to check if they are facing the target:

private bool IsFacingOther(Transform other)
{       
    if (Vector3.Dot(transform.forward, (other.position - transform.position).normalized) == 1)
    {
        return true;    // Return true if facing target.
    }           
    return false;
}

[Nerucius]

Issue done in parallel with #162.

Pull Request at #180

[Nerucius]

Merged at #180