Fix KVM build
Switch to "build core from scratch"

The "-c" option is now modified to allow specifying a generic core...
"-c <ImageScripts dir>/core.gz" reverts to the previous behaviour
Fix OpenVswitch build

The script contained some errors due to cut'n'paste :)
Fix core preparation on modern 64bit architectures

The code was trying to copy a file in non-existent directories
Build "ip" from source
Build "ethtool" from source