This commit adds a many2one between barcode.nomenclature and res.company
and removes Many2one pointing toward a nomenclature record.

This aims to improve the usability and allows using nomenclature in
inventory adjustment where a `nomenclature_id` field was set.

* LDAP import: python-ldap is not python3-compatible, pyldap is

  Warning: only supported from debian Stretch (current testing)?
  https://packages.debian.org/search?searchon=names&keywords=pyldap

* implicitly relative imports
* imports of moved or removed stdlib modules

issue #8530

For a model to use it, it must :
- Inherit barcodes.barcode_events_mixin and override on_barcode_scanned(self, barcode)
- Add <field name=barcode_scanned widget=barcode_handler/> to each form view that
  should listen to barcode events and trigger on_barcode_scanned.

The method on_barcode_scanned works just like an onchange.

Let 2015 be a year without modelines!
cf #4174