[FEATURE] Wizard to add OpenID to backend user

Adds an OpenID wizard button to the be_user's tx_openid_openid field.

The wizard allows to enter an OpenID URL, processes the OpenID login
and finally sets the OpenID in the backend user edit form and
backend user settings form.

This helps registering OpenIDs of providers that hand out different
claimed OpenID URLs for each domain, like Google does.

Resolves: #49310
Releases: 6.2
Change-Id: I953bcfc0df640dc7632f4b78b43f7945606cb7e9
Reviewed-on: https://review.typo3.org/21621
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Helmut Hummel
Tested-by: Fabien Udriot
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind