[thunderbird] Default browser is no longer read from prefs

[Kevin Kofler]

Christopher Aillon wrote:
> Now, we're setting _gsettings_ keys in control center, so those gconf
> keys aren't getting updated when the user toggles that.  But it doesn't
> matter.  I pushed an update to the default gconf values to launch
> gvfs-open as the default browser which will read the values out of
> gsettings.

Shouldn't we use xdg-open instead of gvfs-open? xdg-open will do the right 
thing also under other desktop environments.

        Kevin Kofler