[REF] 8.0 mgmtsystem_action

The current module inherit `crm.claim` while the `state` attribute doesn't exist anymore. I made some changes to use the `stage_id` instead but I'm not so sure it's a good idea. I'm open to suggestions.
The functionality here looks like something that we should try to merge in odoo 8.0, seems central to `crm.claim` not just actions