[FIX] web: correct display of dropdown arrows in ie11
[MERGE] forward port of branch 7.0 up to 8e76938
[FIX] crm_partner_assign: colors only if there is a stage on the lead
[FIX] calendar: avoid to pass ids as string to unlink and write methods

opw-616532: if the event is associated somehow to a workflow, an assert is done to check that element of the ids list are (int, long)
[MERGE] forward port of branch saas-3 up to 2c1bcfb