Add (original, large, medium, small) image URLs for all 1M photos

This pull request adds original (and other) image URLs for all 1M photos in the British Library Flickr Commons manifest. The following modifies all the .tsv files to include the following keys:

* flickr_original_source
* flickr_original_height
* flickr_original_width
* flickr_large_source
* flickr_large_height
* flickr_large_width
* flickr_medium_source
* flickr_medium_height
* flickr_medium_width
* flickr_small_source
* flickr_small_height
* flickr_small_width

Arguably this is overkill and causes unnecessary bloat because:

* Height and widths for only the originals could be included and the others derived as needed
* Height and width could be combined in to a single key
* Individual photo sources could be stored as "parts" (photo farm, photo server, secret, original secret, etc.) thus saving bytes which add up if there are 1M photos

I did not do any of these things since they are all changes that can be applied to the current patch if needed and because they impose a extra layer of understanding and potentially programming in order to use the data dump to fetch an individual photo.

Note: If past experience is any guide there are probably too many changes for a pull request of this size to be merged in the GitHub web application. If this pull request is merged it will likely need to happen from the command line.

Cheers,