Just run the tool on startup, as desktops don't do it for us anymore,
and don't give any feedback as it really is supposed to be completely
invisible action. gsettings-data-convert takes care of not running
it multiple times for a user by itself.
Note that this works only if new schemas and the .convert file are
installed to the system - meaning if doing local testing, it won't
work without installing those system-wide (and updating compiled
schemas) and use the defaults instead; and if then doing that later,
it'll overwrite the settings again from gconf.