district: Refactor models and reset and squash migrations

district/migrations/0001_initial.py

district/migrations/0002_districtarticles.py

district/migrations/0003_auto_20201007_1410.py

district/migrations/0004_districthomepage_donation_page.py

...ct/migrations/0005_districthomepage_footperson_contact.py

district/migrations/0006_auto_20201014_1230.py

district/migrations/0007_auto_20201014_1232.py

district/migrations/0008_districtcontact.py

district/migrations/0009_auto_20201014_1343.py

district/migrations/0010_districttags.py

district/models.py