feature: qt3scan save scan range data

[gadamc]

Currently we just save the numpy array of the scan without the scan axis positions.

We could fix this through a few ways.

1. provide a 'save scan parameters' function / button that saves params to a .json file
2. in the current save function, simply save a new file with the same basename, but with .json extension that contains the scan parameter
3. save a data structure that isn't a numpy array, but instead a single .json file with all of the data in a single file.

[gadamc]

Other options.

In the 'save' function, we could add another file type option of '.json' or '.pickle'. When those are selected, we package the data array along with the xmin, xmax, ymin and ymax values in a dictionary and serialize those to disk.