remove a few minor memory leaks

Mesh/Field.cpp

@@ -1393,6 +1393,10 @@ FieldManager::FieldManager()
   map_type_name["MaxEigenHessian"] = new FieldFactoryT<MaxEigenHessianField>();
   background_field = -1;
 }
+FieldManager::~FieldManager(){
+  for ( std::map<std::string, FieldFactory*>::iterator it = map_type_name.begin(); it!=map_type_name.end(); it++)
+    delete it->second;
+}
 
 #if defined(HAVE_POST)
 void Field::putOnNewView()

Mesh/Field.h

@@ -94,6 +94,7 @@ class FieldManager : public std::map<int, Field*> {
   int newId();
   int maxId();
   FieldManager();
+  ~FieldManager();
   int background_field;
   // compatibility with -bgm
   void setBackgroundMesh(int iView);