The following optimizations were done:
* instead of calling calcCenter() and calcTopFarLeft() just do the halfScale/Scale math on each component individually, this dropped us from about 5.5% of total running time to 1.6% of total running time.
* pass result by reference to save on glm::vec3 constructors which dropped us from 1.6% of total running time to 1.1% of total running time

============
**Before**
```
Running Time	Self		Symbol Name
 44752.0ms    5.5%	5396.0	 	  ViewFrustum::getFurthestPointFromCamera(AABox const&) const
 21106.0ms    2.6%	3006.0	 	   AABox::calcCenter() const
 12892.0ms    1.5%	2095.0	 	   AABox::calcTopFarLeft() const
```
**After**
```
Running Time	Self		Symbol Name
3957.0ms    1.1%	3034.0	 	  ViewFrustum::getFurthestPointFromCamera(AABox const&, glm::detail::tvec3<float, (glm::precision)0>&) const
 618.0ms    0.1%	618.0	 	   AABox::getScale() const
 305.0ms    0.0%	305.0	 	   AABox::getCorner() const
```