Incidents CRUD

This contains 1174, 1178, 1177, 1179 and 1180 (incidents CRUD tickets).

Note: I've tested the basic crud functionality here but have not looked at the incident reports section. That will be much easier to test when we have the capability to assign reports to incidents.
Things like this will eventually end up in an I18n dictionary file. If we do much more stuff like this it might make sense to start using that system right now even if only partially, and storing the keys (e.g. 'new', 'working', ...) as an array.