Re-engineered changes to interpretAtomList from last but one commit

I have added a function that is a non-static member to ActionAtomistic called interpretAtomList.
This non static version means that you can use interpretAtomList in the old way (the function
is a call to the static function that I implemented).  You can thus continue to use interpretAtomList
in the old way or, if you want to call the method from a class that doesn't inherit from ActionAtomistic
you can call the static version of the function

src/core/ActionAtomistic.cpp

@@ -225,6 +225,10 @@ void ActionAtomistic::parseAtomList(const std::string&key,const int num, std::ve
   t.resize(0); interpretAtomList( strings, xpos, this, t );
 }
 
+void ActionAtomistic::interpretAtomList(std::vector<std::string>& strings, std::vector<AtomNumber> &t) {
+  interpretAtomList( strings, xpos, this, t );
+}
+
 void ActionAtomistic::interpretAtomList(std::vector<std::string>& strings, const std::vector<Value*>& xpos, Action* action, std::vector<AtomNumber> &t) {
   Tools::interpretRanges(strings);
   for(unsigned i=0; i<strings.size(); ++i) {

src/core/ActionAtomistic.h

@@ -138,6 +138,8 @@ class ActionAtomistic :
   void parseAtomList(const std::string&key,std::vector<AtomNumber> &t);
 /// Parse an list of atom with a numbred keyword
   void parseAtomList(const std::string&key,const int num, std::vector<AtomNumber> &t);
+/// Interpret the atom selection.  Just a wrapper to the static function with four arguments called interpretAtomList that passes xpos and this.
+  void interpretAtomList( std::vector<std::string>& strings, std::vector<AtomNumber> &t);
 /// Convert a set of read in strings into an atom list (this is used in parseAtomList)
   static void interpretAtomList( std::vector<std::string>& strings, const std::vector<Value*>& xpos, Action* action, std::vector<AtomNumber> &t);
 /// This gets std::vector that contain the PLMD::Value objects that contain xpositions, ypositions, zpositions, masses and charges

src/core/Group.cpp

@@ -156,7 +156,7 @@ Group::Group(const ActionOptions&ao):
     std::vector<AtomNumber> add;
     std::vector<std::string> words;
     words.emplace_back("@ndx: " + ndxfile + " " + ndxgroup);
-    interpretAtomList(words,xpos,this,add);
+    interpretAtomList(words,add);
     atoms.insert(atoms.end(),add.begin(),add.end());
   }
 

src/generic/DumpMassCharge.cpp

@@ -123,9 +123,7 @@ DumpMassCharge::DumpMassCharge(const ActionOptions&ao):
   parseAtomList("ATOMS",atoms);
 
   if(atoms.size()==0) {
-    std::vector<Value*> xvals,yvals,zvals,masv,chargev;
-    std::vector<std::string> strvec(1); ActionAtomistic::getAtomValuesFromPlumedObject(plumed,xvals,yvals,zvals,masv,chargev);
-    strvec[0]="@mdatoms"; interpretAtomList( strvec,xvals,this,atoms );
+    std::vector<std::string> strvec(1); strvec[0]="@mdatoms"; interpretAtomList( strvec,atoms );
   }
 
   bool only_masses = false;