Added tool to add a suffix to all open files

It is now possible to automatically add a suffix to
all the files opened through the Action::fopen tool.
Opening is done as follows:
First the file+suffix is tried.
In case of error the file without suffix is tried.

In this manner, it should be possible to provide a single
input file also for replica exchange stuff. For output files,
it should make any difference.

I also added a stupid keyword to test this feature. Just use
_SET_SUFFIX pippo
in the plumed.dat file to add a suffix pippo to opened files

src/Action.cpp

@@ -31,7 +31,13 @@ Action::Action(const ActionOptions&ao):
 }
 
 FILE* Action::fopen(const char *path, const char *mode){
-  FILE*fp=std::fopen(const_cast<char*>(path),const_cast<char*>(mode));
+  std::string mmode(mode);
+  std::string ppath(path);
+  std::string suffix(plumed.getSuffix());
+  std::string ppathsuf=ppath+suffix;
+  FILE*fp=std::fopen(const_cast<char*>(ppathsuf.c_str()),const_cast<char*>(mmode.c_str()));
+  if(!fp) std::fopen(const_cast<char*>(ppath.c_str()),const_cast<char*>(mmode.c_str()));
+  assert(fp);
   files.insert(fp);
   return fp;
 }

src/PlumedMain.cpp

@@ -316,6 +316,10 @@ void PlumedMain::readInputFile(std::string str){
     if(words.size()==0)continue;
     else if(words[0]=="ENDPLUMED") break;
     else if(words[0]=="LOAD") load(words);
+    else if(words[0]=="_SET_SUFFIX"){
+      assert(words.size()==2);
+      setSuffix(words[1]);
+    }
     else if(words[0]=="INCLUDE"){
       assert(words.size()==2);
       readInputFile(words[1]);

src/PlumedMain.h

@@ -77,6 +77,9 @@ private:
 /// These are the action the, if they are Pilot::onStep(), can trigger execution
   std::vector<ActionPilot*> pilots;
 
+/// Suffix string for file opening, useful for multiple simulations in the same directory
+  std::string suffix;
+
 public:
 /// Flag to switch off virial calculation (for debug)
   bool novirial;
@@ -124,6 +127,10 @@ public:
   void exit(int c=0);
 /// Load a shared library
   void load(std::vector<std::string> & words);
+/// Get the suffix string
+  const std::string & getSuffix()const;
+/// Set the suffix string
+  void setSuffix(const std::string&);
 };
 
 /////
@@ -139,6 +146,17 @@ Atoms& PlumedMain::getAtoms(){
   return atoms;
 }
 
+inline
+const std::string & PlumedMain::getSuffix()const{
+  return suffix;
+}
+
+inline
+void PlumedMain::setSuffix(const std::string&s){
+  suffix=s;
+}
+
+
 }
 
 #endif