- try to re-use existing OffHook session
- hold active lines before: newcall, resume
- allow endcall on: offHook, afterFirstDigit
- allow newcall on: connected, ringin

Also rework a bit softkey sets

Called POV already implemented

- Use thread for: keepalive, receive and send
- Run indefinitevly

If party_id is 0, the phone will not properly release media

double unlock is same as locking :P

Fixes: reloadxml blocked

Because of uninstancied listener

- Solve deadlock:
  + associate all skinny_profile_find_session with the corresponding
    switch_core_session_rwunlock
  + lock the newly created session in skinny_create_ingoing_session
  + enhance rwlocks debugging
- Shared lines:
  + Inform shared lines on answering
  + Answering line has info after other shared lines

flush can be called several times

Merge made by -s ours