Update changelog from 2.0rc6

See merge request !735

(cherry picked from commit e7f647bf)
(cherry picked from commit 3b3ed902)
(cherry picked from commit ca6481d1)
(cherry picked from commit 501a1d6a)

Fix dependency django-phonenumber-field

See merge request !734

Fix and cleanup changelog

See merge request !732

Make admin from/contact settings default to initial superuser

See merge request !727

Resolve "Deleting persons is impossible"

Closes #487

See merge request !728

Set version for django-dynamic-preferences to ^1.11 to include fix which makes deleting persons possible again

Resolve "ALLOWED_HOSTS violations are too loud"

Closes #517

See merge request !731

Resolve "JSON config files not handled"

Closes #516

See merge request !729

Update lockfile

See merge request !725

Resolve "Remove anonymizer for now"

Closes #512

See merge request !720

Resolve "Broken get_*_scopes API for OAuth"

Closes #513

See merge request !721

Resolve "[OpenID Connect] Group claim"

Closes #510

See merge request !718

Update dependency django-bleach to ^0.8.0

See merge request !715

Resolve "Imprint missing in footer"

Closes #502

See merge request !713