ZFS properties on jail creation

[gronke]

It should be possible to define ZFS properties on jail creation. This could be for instance the compression or mountpoint overrides.

An implementation should generically catch ZFS properties, rather than providing a selection of possible properties.

[igalic]

in my eyes, this is related to #413, and also my comments in #630

[gronke]

ZFS properties can be set on creation or modified later with ZFS. Because the exports are using rsync this information would be missing after re-importing a jail and thus need to be added to the ResourceBackup module.