7.0 export partner and address

Completion of the magentoerpconnect_export_partner module to fix the export of partners and add the export of addresses.

This PR depend of this one and need to be merged after : 

* [ ] https://github.com/OCA/connector-magento/pull/33

Initial proposal on lauchpad : 
https://code.launchpad.net/~akretion-team/openerp-connector-magento/7.0-export-partner-and-address/+merge/224180
The problem is that rel_binder.to_backend(binding_id) return False, because it is a new binding.
But it does not return None. So I am wondering if we could change the condition by : 
if not rel_binder.to_backend(binding_id):