[IMP] mass_mailing: option to keep sent emails
[IMP][TEST] event: auto confirmation option, allowing to
automatically confirm events. In a simple flow it is usefull to automatically
confirm event and registrations.

[TEST] event: moved draft2done test into a unittest, easier to finely tune
in order to test the auto confirm option. Moreover this gives a basis to
further add python tests in the module. Hooray.
[IMP] event: refactored event form view. Usability reviews
showed that the form view was complicated and difficult to use. Now
that stat button and edition options in the front-end exist, it is
possible to remove some of the numerous tabs as well as some options
from the form view.

Coming: further cleaning of the model, behavior and probably the various
event-related views.
[FIX] Package: Windows: service name in setup.nsi
[CLEAN] event: lint / remove dead code
- event.event: removed is_subscribed
- event.registration: removed log_ids
- res.partner: removed speaker boolean field, used nowhere
- linted the event module