Make it possible to select a contact from a drop-drop (Contact ID field, combined with logged-in user)

Fix detection of activity fields. Core's checkContactActivityProfileType does not work if we have only one field type

Fixes mixed-entity type profiles, and fixes when a custom field is disabled but still present in the profile

Adds a few improvements to make sure that remoteform can handle formatting, contact-reference fields, groups field, etc.

Add an admin UI for the activity type, and fix the profile submission when the activity type is not atype=1.