Implement --restore-properties and --target-properties

[Peter2121]

Following issue #972 The implemented features permit to define the properties for destination dataset without loosing the initial properties that can be restored later. For example, it is now possible to safely backup and restore datasets with different 'mountpoint' and 'canmount' options. It could be useful to backup the whole 'zroot' dataset to another host and then restore it, without manually changing any option on backup and on restore.