add --outPSL option to liftover.  writes 0s for cols 5 thru 8 since i dont understand them.
add missing tStart index to writePSL
store qSequence offset in psl extra struct.  use to make sure qStarts are written relative to sequence. fix bug where qBlock starts were mixed up between relative and absolute
add validatePSL function to catch some basic errors
overhaul liftover especially block logic.  also fix psl.  add psl validator that will throw exception or assert if it sees a problem
some fixes for reverse strand coorsinates
add end postion to iterator print
Merge remote-tracking branch 'origin/chains' into liftover