message: QuadratureFunction comment improvements
diff: namespace mfem
  {
  +/// Represents values or vectors of values at quadrature points on a mesh.
  class QuadratureFunction : public Vector
  {
  protected:
  - QuadratureSpaceBase *qspace; ///< Associated QuadratureSpaceBase object
  - bool own_qspace; ///< QuadratureSpaceBase ownership flag
  - int vdim;
  + QuadratureSpaceBase *qspace; ///< Associated QuadratureSpaceBase object.
  + bool own_qspace; ///< Does this own the associated QuadratureSpaceBase?
  + int vdim; ///< Vector dimension.
  public:
  + /// Default constructor, results in an empty vector.
  QuadratureFunction() : qspace(nullptr), own_qspace(false), vdim(0) { }
  /// Create a QuadratureFunction based on the given QuadratureSpaceBase.
  