Merge pull request #421 from petrjasek/feat-workflow

feat(workflow): add initial state/action registration
[SD-1217] Backend: All ingested items will have the state ingested
[SD-1214] Created an enum for states and actions
Merge branch 'feat-workflow' of https://github.com/superdesk/superdesk-server into feat-workflow
[SD-1214] Created a static list for states and actions