HMC bit repro across checkpoints. Fixed parallel RNG issue with threading.

Conclusion: c++11 distributions not thread safe and must us distinct dist as well as distinct engine
per site. Makes sense when you think of box muller. Also added a reset of dist on fill to ensure
repro across checkpoints.

lib/algorithms/iterative/ConjugateGradient.h

@@ -30,7 +30,7 @@ public:
       
       //Initial residual computation & set up
       RealD guess = norm2(psi);
-      assert(std::isnan(psi)==0);
+      assert(std::isnan(guess)==0);
 
       Linop.HermOpAndNorm(psi,mmp,d,b);