Django-letsagree

Added support for Django-4.1 started testing for Python-3.11

Added support for Django-4.0 started testing for python-3.10, stopped testing for python-3.6 and python-3.7 (not supported by Django-4.0).

Minor code updates for Django-3.2.
Dropped support for python-3-5.

Initialize `modelformset_factory` within the `FormView` instance instead of using the class variable `form_class` because `get_language()` has a context only within the request/response cycle.

* https://code.djangoproject.com/ticket/31911#ticket
* https://github.com/matthiask/django-translated-fields/issues/24#issuecomment-678069602

Fixed bug in LETSAGREE_LOGOUT_URL setting.

Deprecated `LETSAGREE_LOGOUT_APP_NAME` in favor of `LETSAGREE_LOGOUT_UR`.