This "breaks" the use case of receiving an unencrypted send into an encrypted receiver by setting the receiver's `root_fs`'s `encryption=on`.
"breaks" in air-quotes because we have not yet released a version of
zrepl with encrypted send support.
We will bring back the featured outlined above in a future release.
See https://github.com/zrepl/zrepl/issues/342#issuecomment-657231818 and following.
config defines a single datastructure that can act both as a Map and as a Filter
(DatasetMapFilter)
Cleanup wildcard syntax along the way (also changes semantics).
