refactoring.

 & servers

Presence notificaton for IP2IP
DBUS methods for publishing presence
Adding phone status (ringing,on the phone,ready)

This code enable presence subscription / notification based on Asterisk hint mechanism.
The presence of a SIP account will be automatically pushed by Asterisk server.
DBus interface in CallManager (subsribePresence) is added to subscribe the presence of a buddy uri for an accountID.
Then presence notification are received in buddysip.cpp. Callback to UI must be there implemented.
Lot of commented code is still in the code. Work must be done to clean it.

checkAudio() was being called before the call was removed from the
call list.

Namely by telling the client who triggered recording whether or not
recording has started.

This allows other applications to resume audio.

This went away in 638727ac

Only account uses it.

Remove redundant check of currentCallId, unused codecName and
make currentCall const.

NULL Check calls before trying to answer them