* Only export to remotes that were initialized to support it.
* Prevent storing key/value on export remotes.
* Prevent enabling exporttree=yes and encryption in the same remote.
SetupStage Enable was changed to take the old RemoteConfig.
This allowed only setting exporttree when initially setting up a
remote, and not configuring it later after stuff might already be stored
in the remote.
Went with =yes rather than =true for consistency with other parts of
git-annex. Changed docs accordingly.
This commit was supported by the NSF-funded DataLad project.
28e2cad849