Made “Ha” the only possible option for Hartree to make it consistent

regtest/basic/rt-atomic-units/plumed.dat

-UNITS LENGTH=Bohr TIME=atomic ENERGY=Hartree
+UNITS LENGTH=Bohr TIME=atomic ENERGY=Ha
 d1_bohr: DISTANCE ATOMS=1,2 NOPBC
 d2_bohr: DISTANCE ATOMS=1,6 NOPBC
 d1_angs: CUSTOM ARG=d1_bohr FUNC=0.52917721067*x PERIODIC=NO

src/tools/Units.cpp

@@ -50,8 +50,7 @@ void Units::setEnergy(const std::string &s) {
     energy=0.001;
   } else if(s=="eV") {
     energy=96.48530749925792;
-  } else if(s=="Hartree" || s =="Ha") {
-    energyString="Hartree";
+  } else if(s =="Ha") {
     energy=2625.499638;
   } else {
     energy=-1.0;