Implement audio video conferencing dial-out if conference must immediately start (start time in SDP is 0)
- the body of the INVITE sent out by the server has three parts:
  - SDP
  - resource list with the list of participants
  - SIP frag with the organizer of the conference

Move resource list and sip frag parsing function to the factory

Always clear devices when destroying participant

Change RTP port range of lise_rc

Do not move from transition call state (Updating, Pausing, Resuming) if there are updates yet to be accepted

Set participant device state to Left when receiving a NOTIFY to inform the core that he/she has definitiely left the conference

Improve conference documentation:
- linphone_conference_get_participant_list and linphone_conference_get_participants do not include the local participant (me)
- linphone_conference_get_me() returns the local participant