Fixed wrong AudioTransport attribute name in sip_audio_session.py

darcs-hash:20081208084944-58103-762b779d5946093b012a4e6e03975fae6022ba22
made cpim module use SIPURI; fixed a problem with invalid uri in CPIM From header

darcs-hash:20081208095103-b2873-8e31c813b3ffbcca2450d41f26ad96bf9170adfc