Thermodynamics: Changed all eEqn to EEqn and reformulated to conserve E in sonic solvers

To support these changes the need for "Sp" corrections on div-terms has been
eliminated by introducing a "bounded" convection scheme which subtracts the Sp
term from the selected scheme.  The equivalent will be needed for the ddt term.

A warning message is generated for steady-state solvers in which the "bounded"
scheme is not selected for the convection terms.

tutorials/compressible/rhoCentralFoam/shockTube/constant/polyMesh/boundary

@@ -26,6 +26,7 @@ FoamFile
     empty
     {
         type            empty;
+        inGroups        1(empty);
         nFaces          400;
         startFace       101;
     }