Modify changeProfile to always work on the Profile::Ptr arg it's called
on,this is needed to be able to call setProfile from EditProfileDialog
aftersaving the fallback profile; the fallback profile is special in
many ways,most important of which is that it's never saved to a .profile
on disk, sincechangeProfile is going to give the newly saved profile a
unique name, e.g."Profile 1", we need to update the EditProfileDialog
with the new profile,so that saving settings works and actually modifies
the new profile ratherthan the fallback one. This also means that the
profile ptr that the currentSession is using will point to the
modified/saved profile and not thefallback one.

After the fallback profile is "saved" to a new profile, we init another
instance of the fallback profile, so that it's always availabe in the
"Switch profile" context menu.

Reserve the profile name "Default" for the fallback profile.