/ was missing in the profile entity $ref

closes #7835

This feature only worked on the same pod and was more confusing than
useful.

This commit introduces changes to the user data export archive format.
This extends data set which is included in the archive. This data can be
then imported to other pods when this feature is implemented.

Also the commit adds the archive format json schema. ATM it is used in
automatic tests only, but in future it will also be used to validate
incoming archives.