Adding Shiny frontend for data downloading

[Former user]

As discussed in our email echanges, I think it would be a good addition to QuantTools to add a Shiny application to make the data downloading process more user friendly. I already developped something along that line. You can find it here: http://www.thertrader.com/2016/04/21/introducing-fidlr-financial-data-loader/

Best,

Arnaud