Save and restore tab positions
Bug description
Tabs opens in other order compared to the order they were in when gajim was closed.
Steps to reproduce
Open gajim
Open a few tabs/contacts
Notice the order of the tabs
Quit gajim
Start gajim
Notice how the order of the tabs has changed
Software versions
OS version: Windows 7, Ubuntu 14.04
GTK version: 3.18.9
PyGTK version:3.18.2