CWM12 — Make ChangeRequest useful

This should be part of BusinessInformation: it is not at all specific to WarehouseOperations since one could request changes to database schemas, transformations or pretty much anything.

'isActive' would be better than 'completed' for ChangeRequest, and would observe the convention of using 'is' for booleans. Moreover it should be a derived nonchangeable attribute to avoid inconsistency with 'status'.

The reference from ChangeRequest to ModelElement should be 0..* since the request might be to create something new that cannot yet be referred to!

The following are considered essential for most ChangeRequests: 1) two multivalued optional references to ResponsibleParty to indicate: a) raiser b) actionee 2) optional single-valued integer attribute 'priority' (larger value = more important), constrained to be non-negative. 3) optional single-valued string attributes 'raisersIdentifier' and 'identifier' (representing an id allocated by the raiser and that used internally by the warehouse management system). 4) optional multivalued string attribute 'history' to describe events in managing the request. 5) optional string attribute 'resolution' to decribe what actually happened (e.g. how the modelElements were changed, why the request was rejected etc).