[packagekit] Migrate to GDBus?

[Richard Hughes]

I've got a local branch of PackageKit here that I'm slowly converting
from dbus-glib to GDBus. GDBus is only available in glib 2.25.7, and
that would mean upping the glib dependency.

I'm guessing people would freak out if I merged this into master now,
but wanted to know what kind of timescale I should be working towards.
Should we fork off 0.6.x as the stable branch and start making changes
to 0.7.x unstable branch? I'm currently planning to fork 0.7.0 nearer
Christmas time, although I'm perfectly okay modifying this if anyone
has any other requirements or concerns.

Richard.