[repository] ldap-feed source. Closes #2086984 datafeed based source which copy a subtree of the ldap directory into the system database. Authentication still go through ldap though. Pros: * don't need temporary tables and such for multi-sources RQL queries execution * much more flexible to enhance / configure behaviour (you simply have to replace the parser) * run better when ldap isn't reachable Cons: * no more 'on the fly' discovery of users (though a user authenticating itself will be automatically added if it doesn't exist in the db yet) * synchronization may be heavy if there are a lot of users A new cw.server.ldaputils containing code in common between former ldapuser and new ldapfeed sources has been introduced. Also ldapuser source now uses url instead of custom host/protocol option so it looks like a datafeed source (could be improved).

# type attribute might already be there if migrating from
# version < 3.5 to version >= 3.5.3, BaseTransition being added
# in bootstrap_migration
if versions_map['cubicweb'][0] >= (3, 5, 0):
    add_attribute('BaseTransition', 'type')
    sync_schema_props_perms('state_of')
    sync_schema_props_perms('transition_of')