[libvirt] More java bindings functions

Hello, I just added, because I needed them, two new bindings for java apis: Connection.getCpuStats(int, long) and Domain.getCpuStats(int, long) these two functions act like python's counterpart. I give you the .jar with sources so that, after you review it (it works but I am not entirely sure it is bug free), you could publish it thus helping java programmers who needed a cpu indicator too. Regards, Pasquale Di Rienzo