Reorganize ExpandingMapIterator::readOriginalRow()
Reorganize ExpandingMapIterator::readOriginalRow()

Now doesn't fill the unchanged columns for an original row that
yields no data, since that's wasteful.

wimvanderlinden/Rmodules,cdejonge/Rmodules,cdejonge/Rmodules,thehyve/Rmodules,UMich-Neptune-Transmart/Rmodules,thehyve/Rmodules,thehyve/Rmodules_oncoprint,thehyve/Rmodules_oncoprint,UMich-Neptune-Transmart/Rmodules,baumjamin/Rmodules,thehyve/heim-Rmodules,UMich-Transmart/Rmodules,UMich-Transmart/Rmodules,transmart/Rmodules,baumjamin/Rmodules,thehyve/Rmodules,baumjamin/Rmodules,thehyve/heim-Rmodules,wimvanderlinden/Rmodules,thehyve/heim-Rmodules,wimvanderlinden/Rmodules,transmart/Rmodules,cdejonge/Rmodules,thehyve/Rmodules_oncoprint,UMich-Transmart/Rmodules,UMich-Transmart/Rmodules,cdejonge/Rmodules,wimvanderlinden/Rmodules,transmart/Rmodules,thehyve/Rmodules,thehyve/heim-Rmodules,UMich-Neptune-Transmart/Rmodules,UMich-Neptune-Transmart/Rmodules,baumjamin/Rmodules,transmart/Rmodules