message: Adding sample runs for Kelly estimator in ex15.
diff: // ex15 -m ../data/square-disc.mesh
  // ex15 -m ../data/escher.mesh -r 2 -tf 0.3
  //
  +// Kelly estimator:
  +//
  +// ex15 -est 1
  +// ex15 -est 1 -o 1 -y 0.4
  +// ex15 -est 1 -o 4 -y 0.1
  +// ex15 -est 1 -n 5
  +// ex15 -est 1 -p 1 -n 3
  +//
  // Description: Building on Example 6, this example demonstrates dynamic AMR.
  // The mesh is adapted to a time-dependent solution by refinement
  // as well as by derefinement. For simplicity, the solution is
  // At each outer iteration the right hand side function is changed
  // to mimic a time dependent problem. Within each inner iteration
  // the problem is solved on a sequence of meshes which are locally
  -// refined according to a simple ZZ error estimator. At the end
  -// of the inner iteration the error estimates are also used to
  -// identify any elements which may be over-refined and a single
  -// derefinement step is performed.
  +// refined according to a simple ZZ or Kelly error estimator. At
  +// the end of the inner iteration the error estimates are also
  +// used to identify any elements which may be over-refined and a
  +// single derefinement step is performed.
  //
  // The example demonstrates MFEM's capability to refine and
  // derefine nonconforming meshes, in 2D and 3D, and on linear,
  