WIP backend support for batch creation of locations
Add a dry_run to location batch creation
WIP frontend changes for location batch form
When checking for empty elements, treat empty hashes as empty too.
Implement batch creation of location in the frontend (and tweak the backend to play nice)
Add some warning messages and a spinner to the location batch form
Add selenium tests for the new batch import UI
Merge pull request #457 from hudmol/batch-locations

[Delivers #43561173] Batch creation locations