Converted the array containing atom block indices for the neighbor list from...

Converted the array containing atom block indices for the neighbor list from ushort2 to int.  This removes the hard limit of 2 million atoms.

plugins/rpmd/platforms/opencl/src/kernels/rpmdContraction.cl

@@ -113,6 +113,6 @@ __kernel void contractForces(__global real4* force, __global real4* contracted)
         
         // Store results.
 
-        force[index] = FORCE_SCALE*freal[indexInBlock];
+        force[index] = convert_real4(FORCE_SCALE*freal[indexInBlock]);
     }
 }