Support for Right-Handed Systems about imguizmo

[CedricGuillemet]

it sounds reasonable to me to add a new accessors to set right or left hand.

[timbeaudet]

I was investigating making this change, and I found that changing directionUnary is the singular place it would need to happen, but that is const so a function that takes an index flip couldn't modify it.

void SetRightHandedAxis(int flippedAxis)
{
     directionUnary[flippedAxis][flippedAxis] = -1.0f;
}

Something like this is what I had in mind, though it requires that to be non-const and I don't think that would be a great first change without prior approval.

[timbeaudet]

Upon further testing that change alone wouldn't quite enough, something broke with rotations.