glibmm: Helper classes

# Helper classes
[Generic container converters]

Collaboration diagram for Helper classes:

## Classes
class | Glib::Container_Helpers::ArrayHandleIterator< Tr >
struct | Glib::Container_Helpers::TypeTraits< T >
| Generic TypeTraits implementation. More...
class | Glib::Container_Helpers::ListHandleIterator< Tr >
| If a method takes this as an argument, or has this as a return type, then you can use a standard container such as std::list or std::vector. More...
class | Glib::Container_Helpers::SListHandleIterator< Tr >
| If a method takes this as an argument, or has this as a return type, then you can use a standard container such as std::list or std::vector. More...