steamvr_lh improvements

The following commits enable full body tracking pucks (up to 16 devices total) as generic trackers, logging generic tracker connections in terminal, fixing steamvr reporting zero ipd on start, eliminates history jittering and uses the correct interp on head and hands, and finally hooking up all devices as UNKNOWN until steamvr assigns them a role so as to prevent generic trackers from being assigned as hands although this is yet untested on vive wands.

Do not merge until we can verify vive wands function with UNKNOWN roles assigned out the gate.