#28 download grib data from NOAA server

[cyrille rosay]

downloading grib data should be easier to the user than to have to use a specific tool to download, to save the data in capcode/grib.
capcode should be able to download directly the data for:
- wind à 10 m
- surface pressure
- rain
- on a 0.5 * 0.5 grid
- with up to 7 days forecast
- every 3 - 6 - 12 hours
the area selected would be the area visible on the navigation map.
One the file downloaded, the weather plugin would automatically select this file.