Currently, ekiga uses presence for "presence" status, and "status" the
message, so there is a confusion.

This patch replaces "status" by "note" as following:
set_status -> set_note
get_status -> get_note
std::string status; => std::string note;
status_received -> note_received
schema keys:
  short-status -> presence
  long-status -> presence-note

Notes:
opal uses:
- state = available, unavailable, unchanged, ...
- activities = busy, away
- note = texte in English

SIP specification (rich presence https://tools.ietf.org/html/rfc4480) mentions:
- (basic) status = open or closed
- activities = busy, away
- note

XMPP specification (https://tools.ietf.org/html/rfc6121, sec. 4.7) mentions:
- type = available or unavailable
- show = away, chat, dnd, xa
- status = text in English (custom message in ekiga)