Fix of Lemma export

Modules/FDEM1D/examples/CMakeLists.txt

 add_executable( PolygonalWireAntenna PolygonalWireAntenna.cpp  )
 target_link_libraries(  PolygonalWireAntenna  "lemmacore" "fdem1d")
 
+add_executable( CircularLoop CircularLoop.cpp  )
+target_link_libraries(  CircularLoop  "lemmacore" "fdem1d")
+
 add_executable( EMDipEarth1D EMDipEarth1D.cpp  )
 target_link_libraries(  EMDipEarth1D  "lemmacore" "fdem1d")
 

Modules/LemmaCore/include/helper.h

   static Node encode(const Lemma::Vector3r& rhs) {
     Node node;
     for (int ic=0; ic<rhs.size(); ++ic) {
-        node[0].push_back( rhs(ic) );
+        node["data"].push_back( rhs(ic) );
     }
     node.SetTag( "Vector3r" );
     return node;
         return false;
     }
     int ir=0;
-    for(YAML::const_iterator it=node[0].begin(); it!=node[0].end(); ++it) {
+    for(YAML::const_iterator it=node["data"].begin(); it!=node["data"].end(); ++it) {
         rhs(ir) = it->as<Lemma::Real>();
         ++ir;
     }