Leap Hand as "Render Model" and Overlay Tweaks

[LabeVR]

(Hey its me again, thanks a lot for taking my feedback into consideration, it has made overlay interaction far better, im also sorry for making too many issues on this repo lmao)

As of now, SteamVR does not support Skinned meshes as render models, However it is possible to get around this by making an overlay with the skinnedmesh of the hand that is overlayed above everything else (of course this could be toggled by the user in the settings), Ultraleap already provides some hand meshes in their unity sdk, it would be super nice if the Transparent one were used as it doesn't disrupt the user too much. (@jcorvinus did something like this before)

It would be nice to also have a button on the wrists to hide the button overlay.

[SDraw]

This would require to implement 3D rendering system (mesh loading, skeletal animations, shaders and etc.) in current Qt application, or completely switch to something like Unity.
First option is complete overkill, second option is not applicable (tried to tame Unity before to work on dGPU by default, but it refused to work and was switching GPUs on a fly by on its own as it pleased).