network applet: Fix AP sorting.  Secure AP's were getting bumped to the top
without sorting... only insecure networks were being sorted.  This makes the
sort order thus:

 1) Active connection/remembered connections
 2) All remaining connections in order of strength

This seems to make the most practical sense to me: When you're looking for an
access point, it will nearly always be a stronger signal, and you may not necessarily
care if it's secure or not (and besides, the icon shows secure or not in the list)

Fixes #3271
applets: fix popup menu maximum height calculation for hidpi