Send email to lead and add other changes

hypha/apply/activity/messaging.py

hypha/apply/activity/migrations/0056_add_updated_vendor.py

hypha/apply/activity/options.py

...ply/activity/templates/messages/email/vendor_updated.html

hypha/apply/projects/forms/project.py

...s/application_projects/includes/supporting_documents.html

hypha/apply/projects/views/vendor.py