Added documentation for fields.
Added documentation for fields.

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