[MERGE] forward port of branch 9.0 up to 24eebbd2

addons/account/models/account_invoice.py

addons/account/models/account_move.py

addons/calendar/calendar_data.xml

addons/calendar/calendar_view.xml

addons/crm/base_partner_merge.py

addons/crm/crm_lead.py

addons/crm_partner_assign/security/ir.model.access.csv

addons/gamification/models/goal.py

addons/hr_holidays/hr_holidays.py

addons/hr_payroll/report/report_payslip_details.py

addons/im_livechat/i18n/im_livechat.pot

addons/point_of_sale/point_of_sale.py

addons/point_of_sale/static/src/js/screens.js

addons/product_visible_discount/product_visible_discount.py

addons/report/models/report.py

addons/sale/sale.py

addons/stock/wizard/stock_return_picking.py

addons/stock_account/stock_account.py

addons/web/static/src/xml/base.xml

addons/web_settings_dashboard/views/dashboard_views.xml