update examples to make them work again

Now both centos and debian examples use static DHCP feature.
give Cloubed object instead of ctl to all __init__

All Cloubed classes receive a reference to the instantiated Cloubed
object instead of the VirtController object. This should allow removing
weird class variables in next commits.
removed class methods and vars of StoragePool
removed class methods and vars of StorageVolume
removed class methods and vars of Network
removed class methods and vars of Domain