Add a basic kerberos plugin

For now, just show the fields as text fields, so that kerberos information on users is not lost by FD.

https://gitlab.opensides.be/telecomsudparis/Migration-FusionDirectory-OpenLDAP/-/issues/111

changed milestone to %FusionDirectory 1.4

added PJ1801-0146 label

mentioned in commit 299e5365

added 1h of time spent at 2020-05-19

added To Be Tested packaging labels

mentioned in commit af1113f9

removed To Be Tested label

added plugin-kerberos label

added 30m of time spent at 2020-05-19

mentioned in issue demonstration/demo-dev#17

added telecom sud paris label

changed the description