Added option of managing all accounts in sip_settings

Ignore-this: d5b6f37aeae21bea7359d6529e12d85d

darcs-hash:20090421074418-1e3d8-7f7074e3201aa73364dbb9e5d44d86c2053fbf6a
session2: support MSRPIncomingFileStream

darcs-hash:20090421074401-b2873-d0f13a8f5eb3eee734431a02ed7ec29e84ccbe04