Kiwitcms-tenants

- Turn into proper Kiwi TCMS plugin and install settings overrides under
``tcms_settings_dir/`` (compatible with Kiwi TCMS v8.2 or later)

- does not need ``MENU_ITEMS`` and ``ROOT_URLCONF`` override anymore
- does not need to load ``tcms_tenants`` in ``INSTALLED_APPS`` manually
- only need to specify ``KIWI_TENANTS_DOMAIN`` env variable!
- Require ``tcms_tenants.add_tenant`` permission for ``NewTenantView``
- Reimplement ``NewTenantView`` as ``FormView``
- Refactor ``redirect_to()`` to class based view
- Add tests for admin.py. Closes 5
`Issue 5 <https://github.com/kiwitcms/tenants/issues/5>`_
- Replace ``datetime.now`` with ``timezone.now`` for better support of
installations with enabled timezone config
- Enable pylint. Closes
`Issue 17 <https://github.com/kiwitcms/tenants/issues/17>`_
- Enable flake8

- Update django-tenants from 3.0.0 to 3.0.1. Fixes
`Issue 60 <https://github.com/kiwitcms/tenants/issues/60>`_

- Bump django-tenants from 2.2.3 to 3.0.0
- Tested successfully against Kiwi TCMS v7.3 with Django 3.0

- Set ``tcms_tenants.tests.LoggedInTestCase.tenant.owner.password`` to
"password" so it can be reused by downstream tests

- New translations for Slovenian
- Replace ugettext_lazy with gettext_lazy for Django 3.0
- Start shipping ``tcms_tenants.tests`` to be used by other multi-tenant
add-on packages
- Confirmed working against Kiwi TCMS v7.2

- Document how to configure multi-tenancy
- Document ST to MT migration
- Add helper method ``create_oss_tenant()``
- Internal updates to ``TENANT_APPS`` while testing