ConnectDialog: reorganize advanced settings
ConnectDialog: reorganize advanced settings

This is basically a preparation step for:
- #54 - Alternate nickname
- #57 - Perform commands on connect

We needed a simpler and cleaner structure to be able to add
a bunch of new settings without making the dialog messy.

communi/communi-sailfish,killruana/communi-sailfish,communi/communi-sailfish,communi/communi-sailfish,kimmoli/communi-sailfish