[IMP] Crm: Add tracking mixin to manage utm campaign and add this mixin to mass_mailing, crm_lead and sale_order
[FIX] fetchmail: add api decorator on method connect() to fix issue #980

The method does not follow naming conventions. Therefore the "guessing" api
decorator picks the wrong method wrapper.

(Manual rebase of #1003)
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64