Don't edit the Fallback profile, instead create a new one

This is a first step in simplifying the code; since the Fallback profile doesn't have a file on disk, it's basically a corner-case that we have to babysit in various places in the code.

Now when the user tries to "Edit current profile", if it's the Fallback profile, a new profile is created, with a unique name "Profile 1", "Profile 2" ...etc. This is similar to using the "New" button in the ProfileSettings dialog.