Improve network page

The network page (connect to WiFi) has a couple of problems related to UX, namely:

If wiresless networks are found, their list will not be refreshed; this is a problem if the user needs a network that wasn't detected for some reason (e.g. moving a laptop around, temporarily disconnected router, etc.). When connecting to a network, there's no visual feedback that a connection is in progress. When a connection to a network has succeeded, there's no clear indication of such.

This MR tries to fix those. Ideally we'd have an independent component that we could share with g-c-c so that we could list the networks here and just set an option to hide the settings button, etc. But that would require more time to get done well, so I propose we apply the changes in this MR for now.