replace calls to force->*numeric() with the corresponding utils::*numeric()

this also removes the now obsolete functions from Force

src/compute_pressure.cpp

@@ -90,7 +90,7 @@ ComputePressure::ComputePressure(LAMMPS *lmp, int narg, char **arg) :
 
         if (narg > iarg) {
           if (isdigit(arg[iarg][0])) {
-            nsub = force->inumeric(FLERR,arg[iarg]);
+            nsub = utils::inumeric(FLERR,arg[iarg],false,lmp);
             ++iarg;
             if (nsub <= 0)
               error->all(FLERR,"Illegal compute pressure command");