refactor vpn connection status to be a subset of leap/eip status

Currently we're showing just openvpn status. We must make that a subset of the leap status.

Investigate the use of QFsm for this :)

0. disconnected
1. check network connection
2. check provider
3. check encryption keys
4. connecting to gateway
5. authenticating
6. establishing network encryption
7. connected

(from redmine: created on 2012-09-26, closed on 2012-10-08, precedes #672 (closed))