Correct Optimize.includeOrderFieldsInSelect

The \\ operator on lists only removes as many elements from the LHS as there
are on the RHS.  This was incorrect in this case since a column may appear
twice on the LHS and should be removed if it appears at all on the RHS.

Nubbing solves the immediate problem.  However, Optimize is riddled with
subtle bugs and really needs to be completely rewritten.