Interactive Heatmap: Added option to display column headers as strings.
Interactive Heatmap: Added option to display column headers as strings.

Previously, the column number was displayed.

For now, assumes if the first column header is empty, then that column contains labels.

adsorensen/flow,adsorensen/flow,lukejharmon/tangelohub,Kitware/flow,Kitware/flow,adsorensen/flow,Kitware/flow,Kitware/tangelohub,adsorensen/flow,Kitware/tangelohub,lukejharmon/tangelohub,Kitware/flow,lukejharmon/tangelohub,Kitware/tangelohub,adsorensen/flow