Got rid of some of the hard-coded units in the plumed interface

  // LAMMPS units wrt kj/mol - nm - ps

  // Set up units

  if (force->boltz == 1.0) {

  if(strcmp(update->unit_style,"lj") == 0) {

    // LAMMPS units lj

    p->cmd("setNaturalUnits");

  } else {

    // Conversion factor from LAMMPS energy units to kJ mol-1 (units of PLUMED) 

    double energyUnits=1.0;

    double lengthUnits=1.0;

    double timeUnits=1.0;

    if (force->boltz == 0.0019872067) {

      // LAMMPS units real :: kcal/mol; angstrom; fs

      energyUnits=4.184;

      lengthUnits=0.1;

      timeUnits=0.001;

    } else if (force->boltz == 8.617343e-5) {

      // LAMMPS units metal :: eV; angstrom; ps

      energyUnits=96.48530749925792;

      lengthUnits=0.1;

      timeUnits=1.0;

    } else if (force->boltz == 1.3806504e-23) {

      // LAMMPS units si :: Joule, m; s

      energyUnits=0.001;

      lengthUnits=1.e-9;

      timeUnits=1.e-12;

    } else if (force->boltz == 1.3806504e-16) {

      // LAMMPS units cgs :: erg; cms;, s

      energyUnits=6.0221418e13;

      lengthUnits=1.e-7;

      timeUnits=1.e-12;

    } else if (force->boltz == 3.16681534e-6) {

      // LAMMPS units electron :: Hartree, bohr, fs

      energyUnits=2625.5257;

      lengthUnits=0.052917725;

      timeUnits=0.001;

    } else error->all(FLERR,"Odd LAMMPS units, plumed cannot work with that");

    // LAMMPS units real :: kcal/mol; 

    if (strcmp(update->unit_style,"real") == 0) energyUnits=4.184;

    // LAMMPS units metal :: eV;

    else if (strcmp(update->unit_style,"metal") == 0) energyUnits=96.48530749925792;

    // LAMMPS units si :: Joule;

    else if (strcmp(update->unit_style,"si") == 0) energyUnits=0.001;

    // LAMMPS units cgs :: erg;

    else if (strcmp(update->unit_style,"cgs") == 0) energyUnits=6.0221418e13;

    // LAMMPS units electron :: Hartree;

    else if (strcmp(update->unit_style,"electron") == 0) energyUnits=2625.5257;

    else error->all(FLERR,"Odd LAMMPS units, plumed cannot work with that");

    // Conversion factor from LAMMPS length units to nm (units of PLUMED)

    double lengthUnits=0.1/force->angstrom;

    // Conversion factor from LAMMPS time unit to ps (units of PLUMED)

    double timeUnits=0.001/force->femtosecond;

    p->cmd("setMDEnergyUnits",&energyUnits);

    p->cmd("setMDLengthUnits",&lengthUnits);

    p->cmd("setMDTimeUnits",&timeUnits);