Media over Websocket Channel Driver

Media over Websocket Channel Driver

* Created chan_websocket which can exchange media over both inbound and
outbound websockets which the driver will frame and time.
See http://s.asterisk.net/mow for more information.

* res_http_websocket: Made defines for max message size public and converted
a few nuisance verbose messages to debugs.

* main/channel.c: Changed an obsolete nuisance error to a debug.

* ARI channels: Updated externalMedia to include chan_websocket as a supported
transport.

UserNote: A new channel driver "chan_websocket" is now available. It can
exchange media over both inbound and outbound websockets and will both frame
and re-time the media it receives.
See http://s.asterisk.net/mow for more information.

UserNote: The ARI channels/externalMedia API now includes support for the
WebSocket transport provided by chan_websocket.

(cherry picked from commit aa144106517c28dfb81edb7afc2b60e38c805182)