Satellite filtering

[blychs]

This adds the filtering capabilities for satellite data. I. e., it just takes our existing methods and iterates them over a dict, if needed.

There are a few simple steps that would make it better for version 2, as well as more flexible:

a) We could just have all of this methods as functions in the tool. This way, our filtering, masking, etc., would work for both satellite and surface, which would help us move in a Do Not Repeat Yourself direction and make life considerably easier.

b) If we move out of dicts for satellites, we might be able to call our methods directly. Seems like a long shot, though.

Cheers
Pablo