To ease the marketing and lead follow up, a stat button about
livechat sessions of the lead (that comes from the website_visitor model)
is added to the crm.lead form view.
This button displays and redirect to a list of all the sessions
from all the visitors related to the lead.
Task ID : 2057428
PR #36180
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>
