added a QUASR-downloader

[smiet]

It would be amazing to have all of the QUASR configurations accessible with just one command.

I implemented a simple interface using the 'requests' library, that downloads any QUASR field.

I tried to make it so that it picks a random configuration, but apparently not all integers between 0 and 300,000 correspond to an entry in the database. @andrewgiuliani is there a list of which entries exist, so that a robust random picker can be returned? Or even better, the user could directly query the database for a list of constraints (NFP, A, iota, coil length, etc) and get a random config that fits their needs.

Something like this must be already implemented on the website, one would only have to adapt this to python. I am happy to do this but would need more info on the database itself. Would this be of interest @andrewgiuliani?