Require vertical domain for cubes

[perolavsvendsen]

It is currently allowed to export (seismic) cubes without setting data.vertical_domain. This parameter is required by OpenVDS, and when it is not set, this prevents creation of OpenVDS formats. So cubes cannot be stored in Sumo.

Suggested solution:

• Require vertical_domain to be set (to "depth" or "time") when exporting seismic cubes.

Related:

• Seismic metadata is uploaded but not binary data (following fmu-dataio issue missing key) fmu-sumo-uploader#99