Added methods for obtaining iterators over nodes, edges and faces.
Added methods for obtaining iterators over nodes, edges and faces.

saggita/umeshu,Mattey40/umeshu,lsy176/umeshu,lsy176/umeshu,Mattey40/umeshu,saggita/umeshu,saggita/umeshu,Mattey40/umeshu,lsy176/umeshu