[IMP] display breadcrumbs content in browser tabs

this change is simple, except that many actions display a form view in
'create' mode to edit some stuff (for example, most settings forms or
the 'Your session' action in point of sale).

As a work around, we use
a simple heuristic (nice word for horrible hack): the title displayed
is the title of the action if we have a single form view.
Merge branch 'master' of https://github.com/odoo/odoo into master-linux64