bug fixes in unit tests
Add use external number property for referral
Add new media property for pre-connect message (not implemented)
Updated changelog
Update DDR records for referred calls
first version of preconnect (untested)
fix: return application/xml for twilio endpoints
Merge branch 'release_1.5.0' into develop

Conflicts:
	dialoghandler/changelog.txt
	dialoghandler/src/main/java/com/almende/dialog/adapter/TwilioAdapter.java