Adopt Wikimedia/Mediawiki mobile thumbnail strategy

[kelson42]

The current thumbnailing/resizing strategy is [a custom heuristic]( Re-work image resizing #2101 ) by @audiodude because none of us was able to provide something better than this. But we should mockup the Wikimedi/Mediawiki strategy once we have discovered it and assessed it.

See upstream ticket.

[benoit74]

Note that this problem impact only WikimediaMobile, not WikimediaDesktop for which images are absolutely identical between 1.13 and 1.14.

I just did the check with an old run of 1.13 (still on old mobile API) and a run of 1.14.1 with WikimediaDesktop. All images are purely identical besides additions / modifications in the meanwhile.

Since we are beginning to consider that WikimediaDesktop is the new preferred renderer for Wikimedia wikis, it is worth to keep this information in mind.