Suggestion: Allow downloading CSV from a web location

**Is your feature request related to a problem? Please describe.**
A multi-location or remote team using Git may have datasets stored in different locations which prevents using .mbconfig file for retraining without editing the JSON. Dataset may also be updated and need to be sent for all team members. Ideally, there would be a way to request the latest dataset when starting training.

**Describe the solution you'd like**
One way would be to allow putting a URL in the file path (file source?) of the JSON file.

Model Builder would then download the dataset from that location upon start. It would allow data preparation team to simply update one location with the latest file, and all locations would always use the latest versions. As a copy of the original dataset is anyway made from the origin, so I suppose it could as well be downloaded from an online location.

A bonus would be a simplification of ML.NET tutorials because users could just download the .mbconfig file and just run it.

**Additional context**
This might also allow creation of "training agents" by MS or the community. Agent could just get .mbconfig file and train it.

It should be considered what to do with the file after the training has finished. It might be a good idea to delete it, or ask user if it should be deleted, to not consume disk space with something the user did not explicitly download.

If .mbconfig files would be shared freely, it may be a security concern as the .mbconfig could request to download malicious files. Anyway, I think the benefits outweight the risks at least for data science teams, but the risks may be greater for teams or developer with less need for dataset sharing. Potentially, showing a dialogue "This file requests to download .....Make sure it is trusted location ... OK?" could be enough.