LightDM on Lubuntu

Due to Ubuntu major changes in Oneiric release, we need to adapt our distro too. This will make it easier to develop and debug cross-distro code. So, another change will come to Lubuntu: the greater. Lubuntu will use LightDM, as Ubuntu will do. Obviously I need to polish and make it look good, but I’m sure we’ll be on time to make our Lubuntu prettier and faster.