Allow to have UAC and UAS for a dialog on the same sipapp
Merge branch 'allow-dialog-uac-uas-upstream' of git://github.com/RumataEstor/nksip into dialog2
Minor clean-up
Merge branch 'master' into allow-dialog-uac-uas
Working in dialog behavior in proxies
Tests updates
Fix proxy's dialog behaviour

With the new code, allowing for different dialog's id for uac and uac, the dialog management at proxies is broken.
A proxy behaves in the same request as an uac and a uas, and the dialog id must be the same.
The proxy originates the request as a UAC. If a later in-dialog request comes from the other party, it is used the first dialog id instead of the new one.

A `dialog_id` field has been added to the #sipmsg{} record.
All tests should be passing again.
Minor update
Merge branch 'master' into allow-dialog-uac-uas

Conflicts:
	src/nksip_call_uac_dialog.erl
	src/nksip_call_uac_reply.erl
	src/nksip_call_uas_dialog.erl
	src/nksip_call_uas_reply.erl
	src/nksip_dialog.erl
	src/nksip_uas_lib.erl
	test/ipv6_test.erl
	test/uac_test.erl
Correct errors after merge
Update README.md
Remove 'nksip' parameter in Via

'nksip' parameter was used to detect that a incoming response corresponds to a stateless request we have sent.
Now this information has been added to 'branch' parameter, after a '-'
Updated CHANGELOG.md
Fix error in dialog uac for proxies