PURPOSE
Improve the Email Marketing tour and onboarding to create a "wow effect" when
users test the app.
SPECIFICATIONS
Create a tour for mass_mailing to let user visit Odoo Email Marketing through
a simple mailing creation flow.
This require the following functional changes
* by default, if user chooses to contact mailing lists and there is a single
mailing list available, add it as default value for chosen list;
* create a master mailing list data containing the admin user so that he can
easily follow the tour and test the mailing application;
LINKS
Task ID 2194876
Community PR odoo/odoo#48259
Upgrade PR odoo/upgrade#983
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>