Added possibility of parsing scan positions from json files (key names seem to be more consistent across detectors)
Now recdir argument accepts multiple '%s' (see helpstring, useful when reconstructions go to ra directly)
Added choices to 'units', 'xx_sign' and 'zz_sign' parameters to ensure the CLI throws an error if these arguments are not used correctly.
Added 'valid_scans' parameter to specify a list of strings the parsed paths must contain to be stitched (any of them must be present). It is useful for debugging when there are many scans to stitch.
Commented out the addition of the string '/rec_16bit_Paganin' in L192 since the reconstructions are sometimes named 'rec_16bit_phase' and this can be specified using the 'recdir' parameter.