For each ISO image the individual cdrom device will be added to the VM. During the cleanup these devices will be deleted. It makes attach steps more clear - there is no doubt what is the name of the device. Related to: [mitchellh/packer#1502]
'parallels_tools_host_path' param is deprecated 'parallels_tools_flavor' is added (mandatory).
Also remove floppy and prl-tools ISO if applicable.
Added builder plugins: builder-parallels-iso and builder-parallels-pvm.