more work on admin interface - inline models, naming, conditional viewing etc.

contracts/admin.py

contracts/forms.py

contracts/migrations/0001_initial.py

...ons/0002_alter_contract_all_parties_sign_date_and_more.py

...ts/migrations/0003_alter_contract_public_status_set_by.py

contracts/models.py

shared/models.py

static_src/admin/signee_form.js

webpack.config.js