[IMP] base: Rename res.partner _description from 'Partner' to 'Contact'

Purpose
=======

When using Studio and adding a many2one field for example, it will be easier for a non technical user to find the model res.partner under the name "Contacts" than under the name "Partners".

addons/account/models/partner.py

@@ -200,7 +200,6 @@ class AccountFiscalPositionAccount(models.Model):
 class ResPartner(models.Model):
     _name = 'res.partner'
     _inherit = 'res.partner'
-    _description = 'Partner'
 
     @api.multi
     def _credit_debit_get(self):

odoo/addons/base/res/res_partner.py

@@ -127,7 +127,7 @@ class PartnerTitle(models.Model):
     _sql_constraints = [('name_uniq', 'unique (name)', "Title name already exists !")]
 
 class Partner(models.Model):
-    _description = 'Partner'
+    _description = 'Contact'
     _inherit = ['format.address.mixin']
     _name = "res.partner"
     _order = "display_name"