[packagekit] yum2 backend

[Tim Lauridsen]

I spend some time make the yum2 dbus backend work.

Had to comment out all dbus service methods in the base class 
(deamonBackend.py) because it looks like overloading the methods in 
yumDBUSBackend.py was not working, so when calling the methods from via 
dbus call the stubs in the baseclass, and they are not doing any action.
I have add a call to a self._check_init() in each dbus method, it checks 
if Init() has been called and call it if not, it also setup if we want 
to use the yum cache or not.

Howto Test it using d-feet:

cd backends/yum2/helpers
sudo ./yumDBUSBackend.py

in another console:
sudo d-feet

unfold 'org.freedesktop.PackageKitYumBackend'
double click on 'GetUpdates()' under 'Methods'
press 'Execute'

You can see the result in the console running yumDBUSBackend.py

Tim