Implementation for new ubus call to get call_status

Call Status for each line can be get by:
ubus call asterisk call_status '{ "line" : X }', where X is line:
{0, 1, 2, or 3}

callStatus is set in chan_brcm according to TR-104 requirements:
Idle: no ongoing calls
Dialing: the process of collecting digits for the calling number in an outgoing call, and ringing in outgoing call.
Delivered: N/A
Connected: a call is established
Alerting: ringing when an incoming call is received
Disconnected: the remote party has ended a call. but the local party has not gone on-hook.