Session handling update

Depends on matching commit for svmp-protocol-def.
Added support for receiving, storing, and reusing session tokens from the proxy.
If session tokens are not used, the client falls back to normal authentication.
Added support for receiving a timeout message from the proxy and displaying the
authentication input dialog again.

Change-Id: Ib1a0078f002b0cc519f116f06194140d41d2664a