[packagekit] Heads up: filter changes

[Richard Hughes]

I've changed the filter type from a string to a enumerated type for
PkClient. This means you'll have to rebuild a new PackageKit if you
build gnome-packagekit as the libpackagekit api has changed.

There's no DBUS API break, as all the communication is still done with
easy to understand string types over dbus.

I'll be converting the daemon core to use the filters too, but this will
all be internal.

Richard.