feat(runtime)!: MCOL-678 A "GROUP BY ... WITH ROLLUP" support

Adds a special column which helps to differentiate data and rollups of
various depts and a simple logic to row aggregation to add processing of
subtotals.

dbcon/joblist/tuple-bps.cpp

@@ -3108,6 +3108,10 @@ void TupleBPS::setFE1Input(const RowGroup& feInput)
 void TupleBPS::setFcnExpGroup2(const boost::shared_ptr<funcexp::FuncExpWrapper>& fe,
                                const rowgroup::RowGroup& rg, bool runFE2onPM)
 {
+  // the presence of fe2 changes rowgroup format which is used in PrimProc.
+  // please be aware, if you are modifying several parts of the system.
+  // the relevant part is in primimities/prim-proc/batchprimitiveprocessor,
+  // execute() function, a branch where aggregation is handled.
   fe2 = fe;
   fe2Output = rg;
   checkDupOutputColumns(rg);