we now keep last_status_time, show it in tooltip and information window, ask it (jabber:iq:last, JEP-0012) when we open information window. Fixes #1133

use better varnames [PEP8 says varnames such as l are way bad for maintability and high readability, comment the code, cleanup so it does not hide logic. thanks Yann for explaining the logic

when a child has awaiting events, draw parent with message icon and open chat with this child contact when we dubble click on parent