Fixes to the sync api for oasis uploads

A number of fixes and improvements for the new sync api so that it should now be fully able to handle uploads published from oasises.

• The entry id's provided in the bundle must agree with the automatically generated values, or the bundle will be rejected from import (previously, it was possible to provide any kind of string value as entry id in the oasis metadata file)
• Added the option to keep the bundle_info.json file when importing (true by default). The file will be stored in the root folder of the upload (not the raw folder, as before).
• Removed the old oasis functionality from the post upload endpoint in the fastapi (should not be used when we switch to the bundle-based functionality)
• Corrected handling of published_to (have kept it as a list of strings)
• Fixed an issue with the dataset import, and some minor polishing