message: Even clearer differentiation of ConstrainedSolver from ConstrainedOperator in documenation.
diff: @@ -32,8 +32,8 @@ class ParFiniteElementSpace;
  ( A B^T ) ( x ) ( f )
  ( B ) ( lambda ) = ( r )
  - Do not confuse with ConstrainedOperator, which despite the similar name
  - has very different functionality.
  + Do not confuse with ConstrainedOperator, which handles only simple
  + pointwise constraints and is not a Solver.
  The height and width of this object as an IterativeSolver are for
  the above saddle point system, but one can use its PrimalMult() method
  