#552 Detector non-linearity and reciprocity failure

A basic method to apply any desired non-linearity on an Image has been included to begin with. The non-linearity can be specified by a LookupTable or as a function, possibly with parameters, that can act on NumPy arrays. In addition, it also includes a feature to correct for reciprocity failure. A basic unit test to test these functionalities have also been built.
There are a bunch of lines like this that don't adhere to our usual conventions for widths (100 character) or spacing (usually there's a space after a comma in a list of arguments), so those should all be cleaned up.  You can set your editor to wrap around 100 characters so you don't have to look for it manually.