.desktop file security

[John Tapsell]

<snip>
> 7. On initial login make all desktop file launchers in the desktop dir
> as executable.
>
> For 7, maybe we can share what file to use to see if this has been done
> so that this doesn't accidentally happen twice. Say for instance
> "$XDG_DATA_HOME/.converted-launchers".

I prefered mpyne's approach in just assuming all the current .desktops
are bad.  Make it only a once-off confirmation to the user to convert.
 That should be good enough.

John