De-Pivot should ignore special attributes

Status: New

The De-Pivot operator currently has no option to ignore special attributes.  This is a pain because it means if you have a nominal index or a label, then this must be left out of the attributes that are allowed to proceed through the de-pivot operation if the attributes to be de-pivoted are numerical in nature (as they often will be since de-pivot is commonly used in repeated measures type circumstances).  Otherwise the operator generates an annoying "data type mismatch" error and fails to run.  


There is a manual workaround by creating a copy of the original data, then creating a new numeric id field and substituting it for the original id field (and likewise for any label), then performing the de-pivot, and then rejoining to the original data to restore the original nominal id or label.  However this entire ordeal would be quite needless if the De-Pivot operator can simply be designed to ignore any special attributes (like many other operators) when perfoming the transpose operation.