Allow naming profiles on cmdline

[ldoktor]

With customizable profiles it might be useful to actually name the profiles ourselves, especially when we are using multiple instances of the same profile. One way to do that would be to use the $type[:args] by default while allowing to rename it by $name[:{"type": "$type"}] (or class, backend or whatever key). An example of a DefaultLibvirt profile would be MyProfile:{"type": "DefaultLibvirt"}.