Refs #6078, set default of pivot_by_column to empty string so it doesn't get sent in AJAX requests when not set.
Refs #6078, if pivotBy is used in request for HtmlTable visualization data, set columns to display to all available columns.
Refs #6078, disable pivotting in GetSocials report.
Refs #6078, fixing build.
Refs #6078, fix column ordering bug, if 0 is used as pivotted table column, it is ordered first and not prepended.
Allow .contains assertion to be used in screenshot tests as first assertion and allow .contains to be chained w/ .not property.
Fixes #6078, adding UI unit tests for PivotByDimension feature.