* Added properties active_nodes, and node_index_at_active_cells to ModelGrid.
* Added properties active_nodes, and node_index_at_active_cells to ModelGrid.

== Added ==

* New properties for ModelGrid:
  - active_nodes: The node indices for each active node.
  - node_index_at_active_cells: the node indices for each active cell.



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