Some registration chain updates, related to Issue #80.
1. Added a new option for the "name" of the common space. This creates output files with increased readibility. xfm_to_common.xfm now has a more specific name. This also should take care of point 3 in this issue.
2. nlinFH is now a RegPipeFH instead of the base class, due to an issue with getLastXfm. This is another case where an intermediate class might be useful. (See issue #68).
3. Updated and cleaned up LongitudinalStatsConcatAndResample:
3a. No longer concat and resample from i to common point. i to i+1 stats still calculated and resampled to common space.
3b. Stats now calculated from common space to all other timepoints, as we have been doing with the NYU data.
3c. Generally cleaned up code, removed unnecessary functions and added better ones to streamline reading.