Add support for `__name__` to TFL.Meta.M_Base.New
Add `defaultdict_cb` and `defaultdict_int`

Remove legacy support for pre-2.5 versions of Python.
Add and use `recursion_limit = 2`

Show another level of recursion for `MOM.Attr.Querier.Attrs_Transitive`,
`.Atoms`, `.Unwrapped_Atoms`, `.As_Json_Cargo`, and `.As_Template_Elem`.