Eng 7326 plannode reorder

This pull requests is basically reordering the Projection node and ORDER BY node for step 1. Step 2 will make the Aggregation node and Projection node inline for certain cases.

For some cases we can not reorder the plan node tree for ORDER BY, I regressed it to use the old plans although they are not efficient.
Yes, the last one is even needed for columnrefs for ORDER BY cases like:
Select a, count(*) from T group by a, b order by a, b;

Basically we want to mark which group by column/expression is in Display list and find out the missing ones.