Added a new VM command: <availset> to be used for changing the Availability Set for a VM.

As far as I can see the client currently lacks a way of changing the Availability Set for a particular VM.
I've therefore implemented a new VM command called availset which can be used to set the Availability Set for a specified VM. If the Availability Set does not exist it is created.

I've also extended the helper function createPrettyVMView so as to display both UpdateDomain and FaultDomain for a VM when using the vm show command.