network: Add some debug output

This was helpful in looking at how we deal with 'locally connected'
state currently: Not very well.
Fix headerbar height for the summary page

We have a sizegroup that makes all buttons and the title
have the same size. But since we allow the title to leak into
the margins now, we need to add another non-centered widget
that remains visible in the summary header. Use an empty
label for this.
Add an accessible label to the avatar chooser button