qemu: basic video compression for spice

(only from hand-edited config file, which will be ovrewritten by
subsequent usage of vm configuration webif... :( TODO: complete it! )
qemu: spice: by default, add a compression option

which should optimize multimedia.
Merge branch 'master' into v12n
qemu: path fixes and start working on usb disk
qemu: usbdisk: write config file
qemu: usbdisk: cmdline and doc
New Year Release (bump version to 2013.01)