Adapted sip_session2.py to modified Account notifications

darcs-hash:20090428162116-58103-c1c5dbd1f666579dd87c5ada66c37a7431fb08ca
Removed sipsimple.core.Registration

darcs-hash:20090428162655-58103-7548e8df1ce8c694e9bfe6274e0a36201b489426