CG test written and passes i.e. converges with small true residual

in RedBlack MpcDagMpc, Unprec MdagM and Schur red black solver for
each of.

DomainWallFermion
MobiusFermion
MobiusZolotarevFermion
ScaledShamirFermion
ScaledShamirZolotarevFermion

tests/Test_wilson_cg_schur.cc

@@ -0,0 +1,48 @@
+#include <Grid.h>
+
+using namespace std;
+using namespace Grid;
+using namespace Grid::QCD;
+
+template<class d>
+struct scal {
+  d internal;
+};
+
+  Gamma::GammaMatrix Gmu [] = {
+    Gamma::GammaX,
+    Gamma::GammaY,
+    Gamma::GammaZ,
+    Gamma::GammaT
+  };
+
+int main (int argc, char ** argv)
+{
+  Grid_init(&argc,&argv);
+
+
+  std::vector<int> latt_size   = GridDefaultLatt();
+  std::vector<int> simd_layout = GridDefaultSimd(Nd,vComplexF::Nsimd());
+  std::vector<int> mpi_layout  = GridDefaultMpi();
+  GridCartesian               Grid(latt_size,simd_layout,mpi_layout);
+  GridRedBlackCartesian     RBGrid(latt_size,simd_layout,mpi_layout);
+
+  std::vector<int> seeds({1,2,3,4});
+  GridParallelRNG          pRNG(&Grid);  pRNG.SeedFixedIntegers(seeds);
+
+  LatticeGaugeField Umu(&Grid); random(pRNG,Umu);
+
+  LatticeFermion    src(&Grid); random(pRNG,src);
+  LatticeFermion result(&Grid); result=zero;
+  LatticeFermion resid(&Grid); 
+
+  RealD mass=0.5;
+  WilsonFermion Dw(Umu,Grid,RBGrid,mass);
+
+  ConjugateGradient<LatticeFermion> CG(1.0e-8,10000);
+  SchurRedBlackSolve<LatticeFermion> SchurSolver(CG);
+
+  SchurSolver(Dw,src,result);
+  
+  Grid_finalize();
+}