Handles the contains expression. A ContainsExpression is always about a source S which is a SetExpression and an operand O which is
either an entity, constant or query.
Handles the sort clause expression into a QueryExpression without projection. THis is done by first producing a selectexpression which is then handled
by the SelectExpression handler.
Handles the where expression into a QueryExpression without projection. This is done by first producing a SelectExpression which is then handled
by the SelectExpression handler.