prevent restoring database backups with mismatched versions

Background

As discovered in the field, some users have occasionally restored some databases, but not all of them. In other cases, restores were carried out using a set of export files taken from different exports. This can lead to unusable NXRM instances with an incoherent state.

Acceptance

• Modify the filenames of database exports so it's clear whether they were generated
• Disallow restores from incomplete sets, or sets with mismatched export times