Enable basic conferencing support

Set up basic conferencing support.  Right now I have reserved 6000-6999
as conference rooms (not that we actually need that many, but whatever).

Change-Id: I9acddf4ffedc7f499740184778b8bd67e5b38a4f
Install higher quality sound prompts

Telephone calls are generally 8 kHz.  With VoIP, higher sample rates
are possible.  G.722 is the most common, which is 16 kHz.  Conferencing
supports these higher sample rates, as well.  Make sure we have the
higher quality sound prompts installed as well in case we can make use
of them.

Change-Id: I34921fa6a00720d05113a848bc9f1f94f2200c8b