Fix contact_id var name,  as is sent by remoteforms

See merge request !1

Avoid pseudo-profiles, such as Billing, fixes lack of defaults on a Contribution Page for logged-in users

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.