NOTE: "rowspan" is an opt-in feature, because of its small perf hit (it needs to loop through all row metadatas to map all rowspan), and requires the enableCellRowSpan grid option to be enabled to work properly.

NOTE 2: colspan/rowspan are both using DataView item metadata and are both based on row indexes and will not update neither keep the row in sync with the data. It is really up to you the user to update the metadata logic of how and where the cells should span. (i.e: Filtering/Sorting/Paging/... will not change/update the spanning in the grid by itself)