Factory eingeführt. Template Objekt wird aber noch nicht korrekt angesprochen.
Undefined symbols for architecture x86_64:
  "Factory::s_instance", referenced from:
      Factory::instance() in main.o
  "Factory::objects_", referenced from:
      Factory::instance() in main.o
      Factory::create(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [main] Error 1