Camera tool - orientation + mode display

I also updated line3d to use the position property as a translation rather than as the start position; this allows translations + rotations to work as expected.
I updated it to use the position as a translation rather than as the world position of the start point.  In general I think this is more consistent with treating position/rotation as transforms.  In this particular case I wanted it for creating composite overlays using the `OverlayGroup` (https://github.com/huffman/hifi/blob/camera-display/examples/libraries/overlayUtils.js) helper object that I added.  If the position and rotation properties weren't consistent it would have needed to special-case for Line3D and any other overlays that don't use position & rotation in the same way.