[ldapfeed / dataimport] port ldapfeed parser to dataimport API This makes the code easier to understand and will allow to deprecate the old multi-sources api, based on creation callback through repo.extid2eid. Currently with this patch, modification dates are not checked, hence entities will be systematically updated. We run the import with no hooks, because RQLObjectStore can only add entities to the system source.

[server/test] document expected packages to run ldap tests

[ldapfeed] simplify ldap2attrs * tdict argument is never given * separate value retrieval from setting output (will ease a latter cset)