Updates to registration_chain stats calculations:
1. Removed stats calculation of first time point going to all others.
2. We now calculate stats from average to each other time point instead of to average.
3. Related changes include:
	a. statsAndResample now can calculate regular or chain stats, depending on circumstance.
        b. renamed relevant function to avgToNonAdjacentTimePoint to reflect 2 above.

Also fixed minor bug in calcStats and removed unused import in NLIN.py