[ldap auth] make sure imported passwords from LDAP are encrypted (closes #2583994) When a user is imported from an LDAP source (in ldapfeed or when converting a user from an ldapsource to system one), we may import a clear-text password, which we do not want to do in our system database.

[ldapfeed] don't crash if one specify an unexisting group in the configuration. Closes #2538399

[doc/ldap] update the ldap chapter wrt the ldapfeed source type (closes #2551863)

prepare 3.16

[doc/3.16] complete description of what changed

[rql sources] uses an URL as remote host address for pyro/zmq rql sources, instead of extra configuration parameters. Follows modification of dbapi.connect api. Closes #2539822

[repo sources] move handling of source's url into abstract source as this becomes shared by most sources prepare #2539822

[db-api] rename repo_connect into _repo_connect to mark it private. Closes #2521848

[repository sources] copy source configuration: source's __init__ modify it while config.sources() return a cached dictionary which shouldn't be modified This causes pb since f8aa87a773b2 (though it's unclear why it hasn't been a problem before). Closes #2521848

cleanup repository connect doc: cnxtype is now deprecated / base_url has never been given that way. Follow #2521848