V1.1: Add claim_id to message url

If message is claimed, the returned message href now contains
?claim_id=  part. Also in this commit function for message uri construction
was DRYed and extracted to wsgi.utils module.

Partially-implements: blueprint api-v1.1-response-document-changes
Change-Id: Ic8f1a83dbe11366bad519e6507d074202b2b37dd