* Add type-hints to some of the files in gitlab/v4/objects/
  * Fix issues detected when adding type-hints
  * Changed mypy exclusion to explicitly list the 13 files that have
    not yet had type-hints added.

There are small typos in:
- docs/gl_objects/deploy_tokens.rst
- gitlab/base.py
- gitlab/mixins.py
- gitlab/v4/objects/features.py
- gitlab/v4/objects/groups.py
- gitlab/v4/objects/packages.py
- gitlab/v4/objects/projects.py
- gitlab/v4/objects/sidekiq.py
- gitlab/v4/objects/todos.py

Fixes:
- Should read `treatment` rather than `reatment`.
- Should read `transferred` rather than `transfered`.
- Should read `registered` rather than `registred`.
- Should read `occurred` rather than `occured`.
- Should read `overridden` rather than `overriden`.
- Should read `marked` rather than `maked`.
- Should read `instantiate` rather than `instanciate`.
- Should read `function` rather than `fonction`.

Fix the import ordering using isort.

https://pycqa.github.io/isort/

In gitlab/v4/objects/*.py remove usage of:
  * from gitlab.base import *
  * from gitlab.mixins import *

Change them to:
  * from gitlab.base import CLASS_NAME
  * from gitlab.mixins import CLASS_NAME

Programmatically update code to explicitly import needed classes only.

After the change the output of:
  $ flake8 gitlab/v4/objects/*py | grep 'REST\|Mixin'

Is empty. Before many messages about unable to determine if it was a
valid name.