I have no idea why I originall implemented that crap via string munging.

[MERGE] website_mail_group: cleaning and usability improvement of this web module
- refactored the website templates that were basically impossible to use
- fixed display by thread / date and navigation
- added information about group email, participants, messages, ...

[IMP] website_mail_group: display previous / next message when browsing + take into account thread or date mode.

Some fixes in the image qweb widget + CMS fixes

[FIX] website_mail_group: effectively handle replies_per_page parameter that controls the number of replies to display under each message.

[FIX] website_mail_group: better layout for main mailing lists page: more space for subscribe button

[MERGE][FIX] website_event_track: display speakers name to public users

1st issue:
When an exception was raised, it was badly handled by the website in case of
website_enabled key. The response page was generated without calling super.
The WebRequest object being responsible to rollback the transaction in case
of errors.

2sd issue:
The _failed attribute is required to rollback the transaction in an WebRequest
object. Previously it was only set in the JsonRequest object (which inherit
from WebRequest), replace by call to super. The attribute _failed is now set
in the WebRequest object.

[IMP] [BACKPORT] Converto bzrignore to gitignore, like what has been done in master.

[IMP] website_mail_group: refactored layout of displayed mailing lists and their archive. Should be a bit more easy to use and understand. Todo: fix number of displayed thread / replies, and probably re-do the layout once somebody decides to change everything.

product_id_change set the description with the same behavior as sale orders
product_id_change set the price unit according to the pricelist
_prepare_invoice is split into two sub methods, _prepare_invoice_data and _prepare_invoice_line
_prepare_invoice actually prepare the invoice values instead of directly creating the invoice

[FIX] website_hr_recruitment: Hide unpublished job offers to portal users and employees