PURPOSE
Purpose of this commit is to clean statistics fields definition on crm.team.
Future tasks will improve the use of sales team in crm and first steps is to
clean a bit models linked to sales team.
SPECIFICATIONS
New statistic fields
* ``lead_all_assigned_month_count``: all assigned lead and opportunities
in the last 30 days; used notably for scoring mechanism;
Renaming performed on some statistic fields
* ``unassigned_leads_count`` -> ``lead_unassigned_count``;
* ``overdue_opportunities_count`` -> ``opportunities_overdue_count``;
* ``overdue_opportunities_amount`` -> ``opportunities_overdue_amount``;
All those fields are used for display and management purpose, and are
computed not stored fields. No migration is therefore required.
LINKS
Task ID 2088565 (crm: from onchange to compute)
Enterprise PR odoo/enterprise#7322
Upgrade PR odoo/upgrade#781