Updated client awareness of session expiration

Changed server code to use new Protobuf fields for session max
length and grace period when sending AUTH_OK response to a client.
Co-commits:
svmp-android-client
svmp-protocol-def
Changed proxy Response handling

Updated to proxy data straight through without delay, instead of
unpacking Response messages, while using a log level higher than
'silly' and 'debug'.
Add ICE server username & password fields to config schema

Change-Id: I854b2a94330f6fa85be12a0ddb0c243aa5a42b82