ENH: Clean Segment tubes

. Take unecessary steps out of the while loop
. Stop failing when a tube isn't computed since the program might have to
 run for multiple seeds
. Remove unused arguments (seedScaleMask and seedMask)
. Add empty defaults for seedX and seedPhysicalPoint since one should be
empty if the other isn't
. Remove EXECUTABLE_ONLY
ENH: Use lps coordinates when giving points to SegmentTubes
WIP