Add dataset using the URL of a remote repo

[emptymalei]

We don't only upload datasets, we might also want to load datasets from remote.

Here we propose to add the option to add datasets using the URL.

• Build a Herb from remote data
• Option to add metadata only or download everything.
  • Adding metadata only will only add data to the flora
  • Thus we can not find the dataset folder with the corresponding id.
  • This can be used to decide if a dataset is metadata only or fully downloaded.