Add HSSConnection::get_associated_uris method to retrieve associated URIs from homestead
Updates to use new homestead API
Don't set up P-Asserted-Identity in sprout, as bono now does this.
Determine served user from P-Asserted-Identity if P-Served-User header absent.
Tidy up comment
Give registrar access to HSS connection (required for associated public URI lookup)
Retire --auth parameter as we should just always use the IMS digest authentication mode
Query Associated URIs from HSS on registration
Return P-Associated-URI on response, and only store primary URI in memcached
Add P-Called-Party-Id
Switch to using /associatedpublicbypublic/ URL
Add comment explaining why we're not using the private ID (yet)
Look up AOR in memcached from first associated URI from homestead
Use To header not Request-URI when looking up public user ID
Don't register the authentication module on the edge proxy
Tidy up currently-unused code
Merge dev into sto125
Use proper parser for P-Asserted-Identity, and fix up malformed headers in UT
Merge pull request #92 from Metaswitch/sto125

[Reviewer: Mike] Sprout changes for P-Associated-URI and P-Called-Party-ID