[PRD-4216] Eliminated groupIndex in TotalPageItemCountFunction in favor of the group's ReportStateKey, already managed by the parent class.
Moved the convenience PageGroupValues class to top level so it can be shared by the TotalPageSum function.
Per Thomas, added a check to Group.getName() to return the generated name if the name is an empty string.  This corrected the calculation for items defined the wizard aggregation-type to use "Count for Page".