Enable data download and re-upload

[LukasWallrich]

Users should be able to download filtered data (and configuration info) and then be able to upload a file in the same format to restore data and configuration details (to continue where they left off, and to update/change the data).

• [ ] Enable download (already partly implemented)
• [ ] Enable upload of dataset
• [ ] Enable restoration of settings

[LukasWallrich]

@LukasRoeseler download and upload should now work - feel free to take for bodypositions (at least the download, that is a quick copy-paste job)

[LukasRoeseler]

Great, thank you!