hex: replace nodes_at_column with nodegrid, which is now constructed correctly for a vertically oriented rectangular-shape hex grid
hex: replace nodes_at_column with nodegrid, which is now constructed correctly for a vertically oriented rectangular-shape hex grid

cmshobe/landlab,csherwood-usgs/landlab,cmshobe/landlab,landlab/landlab,Carralex/landlab,amandersillinois/landlab,amandersillinois/landlab,RondaStrauch/landlab,cmshobe/landlab,RondaStrauch/landlab,landlab/landlab,laijingtao/landlab,landlab/landlab,ManuSchmi88/landlab,RondaStrauch/landlab,Carralex/landlab,ManuSchmi88/landlab,ManuSchmi88/landlab,csherwood-usgs/landlab,laijingtao/landlab,Carralex/landlab