Bind incoming INVITE dialog to transport in which request was received

darcs-hash:20090401162351-58103-f0726bd1529c98adc2d1b04508691ccaa47567e9
Fixed default value for SIPSimpleSettings.default_account

Ignore-this: 498b7b17845fab0d7d103383b53c16d8

darcs-hash:20090401142546-1e3d8-be44642f7586d20809abca28841be9f0f426660b