[packagekit] Potential unmaintained backend removals

[Richard Hughes]

Hi all,

I'm going to be clearing out any unmaintained backends that have not
had at least one commit from an author other than me in the last 18
months.

The backends at risk of being removed are:

box:    Apr 2010
opkg:    Jul 2010
conary:    Jun 2011
slapt:    Sep 2011
portage:   Mar 2012
smart:    Jun 2012

If there is no response from the maintainers in 6 weeks (if it's still
works fine with the most up to date distro release and compiles okay,
just let me know) I'll be removing them from master. Comments welcome.

Thanks,

Richard.