Added per account setting to send DTMF inband

darcs-hash:20091204112321-58252-27415b9eae4c62b3c1508f20c60f7bb5d458cf01
Added slot property to AudioStream

Ignore-this: 5d9904d9aa6188d713c710979593aff4

darcs-hash:20091204091505-1e3d8-d4425456db85c8ea048366a6becf8d49505dbcc1