OutputTree more flexibility for output
The following proposal to facilitate output handling:
template <class T>
void addData(typename std::initializer_list<std::pair<std::string, T> > list )
{
for( auto&& elem : list )
set<T>(elem.first, elem.second);
}
(not sure this is 100% correct) So we could output like
outtree.addData({{key1, value2}, {key2, value2},...})