Add canReadList function to show what sources could be used.

[manthey]

import large_image, pprint

pprint.pprint(large_image.canReadList('TCGA-02-0010-01Z-00-DX4.07de2e55-a8fe-40ee-9e98-bcb78050b9f7.svs'))

results in

[('openslide', True),
 ('multi', False),
 ('openjpeg', False),
 ('tiff', True),
 ('deepzoom', False),
 ('nd2', False),
 ('ometiff', False),
 ('tifffile', True),
 ('vips', False),
 ('pil', False),
 ('bioformats', True),
 ('gdal', True),
 ('mapnik', True)]

showing the order and utility of each source.