Enhancement/crop l2a
The L2A output is now cropped to the overlap area of VNIR and SWIR. There are no more image areas that only contain VNIR or SWIR data. This fixes issue #34.
@nbohn @brenner.silva_at_awi.de This is also solves the issue that for some areas of the VNIR no surface reflectance can be computed because parameter retrieval is based on the SWIR data which is missing there (also for the water AC where parameter retrieval is running in the VNIR). Since these image areas are cropped during the generation of the orthorectified image anyways, it does not matter which pixel values you put in there.