Avoid downloading data to Switchboard server

[emanueldima]

Currently Switchboard creates a local copy of the data and sends a url of it to the tools, to avoid possible CORS problems (see #2).

If we can solve the CORS issues (can we?), we should profile the data using a small header (should work with most data types) and send the original url to the tools.

[twagoo]

Proxying could be an alternative to downloading