First complete version of Landsat-download tool

Automatically downloads Landsat images from (http://earthexplorer.usgs.gov/)

Several options are provided, as the possibility of downloading all the scenes of a given scene defined by its Path-Row coordinates, of providing a list of files to download. it is also possible to only download files with less than XX% of clouds, or to unzip the files directly.

This little software was developped by Olivier Hagolle and received contributions by Vasco Nunes and Jake Brinkmann