Add command line options --search-on-r0 to pfindpts miniapp
Add command line options --search-on-r0 to pfindpts miniapp

This option forces only MPI task 0 to own any points to search for, as
opposed to the default behavior where all tasks search for the same
points.  The purpose of this is to test the situation where some MPI
tasks find boundary points, meaning those tasks have points with
gsl_code=1, but other tasks do not.

mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem