Error checking for weather.get

[MDKempe]

Weather.get is one of the most important methods, it need to have a lot of error checking. Specifically, if you use PSM3 it should first check to see if the gid or the lat/lon are valid and in the range of testable area. If not, an error message should come up with a link to where to determine the applicable area or how to properly get the gid. A similar thing should be in place for the other methods using the NSRDB or PVGIS.