receive_resume_token is missing from FilesystemProperties

[asomers]

Is your feature request related to a problem? Please describe.
I need to know if a dataset has a receive_resume_token

Describe the solution you'd like
FilesystemProperties (and VolumeProperties) should have a receive_resume_token method.

Describe alternatives you've considered
The best alternative at this point is to run zfs get as a command

[andoriyu]

Will take a look later this week