Actually use bridging_seq in xform_brain

* this is much cleaner and works …
* but only with a bug fix for streamxform - see
https://www.nitrc.org/forum/forum.php?thread_id=4697&forum_id=857
* so for time being we will have to hold off
consistent ordering of ref/sample arguments

* everyone else has sample then ref (i.e. from, to)
Add explicit checkboth and mustWork arguments
document and export bridging_sequence
update test to reflect new boundingbox class
depend on nat >=1.5.9 for xformpoints.cmtkreg

* since we have devolved handling of compound registrations to xformpoints.cmtkreg
Merge branch 'feature/xform_brain_bridging_seq'

* feature/xform_brain_bridging_seq:
  depend on nat >=1.5.9 for xformpoints.cmtkreg
  update test to reflect new boundingbox class
  document and export bridging_sequence
  Add explicit checkboth and mustWork arguments
  consistent ordering of ref/sample arguments
  Actually use bridging_seq in xform_brain
bump version to 0.3