validation, other cost unit types, unify contractee / signee views, intent desc.

contracts/admin.py

...0025_rename_cost_amount_other_contract_cost_unit_other.py

...acts/migrations/0026_alter_contract_is_public_and_more.py

contracts/migrations/0027_alter_contractintent_options.py

...028_remove_contractee_role_remove_signee_role_and_more.py

...igrations/0029_alter_contracteesignature_role_and_more.py

contracts/models.py

contracts/templates/contracts/view_contract.html

contracts/templates/contracts/view_contractee.html

contracts/templates/contracts/view_signee.html

contracts/views.py

static_src/admin/contract_form.js