Expose all LDAP config options in Crowbar

Allows admins to edit these options in the raw editing mode, it doesn't
make sense to expose all these in the web UI. Also fix the type of
'user_enabled_default' from string to boolean (like upstream).

Needs a schema migration.
Merge pull request #128 from saschpe/release/roxy/master-ldap-expose-all-configs

Expose all LDAP config options in Crowbar