api: remove m9dicts dependency and utilize anyconfig.dicts.* instead
api: remove m9dicts dependency and utilize anyconfig.dicts.* instead

- 'ac_namedtuple' keyword option for load and dump APIs is deprecated
  and removed because it makes implementation complex a lot.
- 'to_container' API is removed because it does not work as expected and
  make implementation complex more than it should be.
- add new API 'merge' to merge normal mapping objects like dicts which
  imported from anyconfig.dicts.
- Merge result dicts with anyconfig.dicts.merge instead of using mapping
  classes in m9dicts.dicts

ssato/python-anyconfig,ssato/python-anyconfig