Feature/safe icicle alternate approach

Again, I'm kind of abusing the pull request process a bit here.  This is another approach to "safe" ICICLE generation for your consideration.  This will work with older versions of libvirt as it does not require domain "external snapshot" features.  Instead it explicitly creates a disposable qcow2 image which is used for collect_setup and ICICLE generation before being deleted.

I actually favor this one as I'll likely be able to reuse the new functions in the LiveCD plugin.  Specifically, it will allow launching a copy of a "utility" image file without having to make a full copy of it.  (Which, I accept, isn't necessarily a good reason why _Oz_ should use one approach or the other.)