Support user agent string with download recipe

Jason

I am trying to download data from some US government websites, and most will allow the download recipe to run without hassle, but a few like the Bureau of Labor and Statistics (BLS) will sometimes return a 403:Forbidden error when trying to download data. I can easily get around this by using CURL or anything else that offers a user agent string as part of the request. Could we add a checkbox that instructs the download recipe to offer a user agent string?