Album art ratios not preserved

[benrr101]

When displaying album art (especially in the metadata editor), the ratio of the art file from the server isn't preserved. This should be addressed by making specific requests to the server for specific sized album art. That way, the ratio is preserved at the server side without the need for any bullshit javascript implemented solutions.

For now, we'll leave the images squished.

This requires a change on Dolomite, and is already a reported issue: benrr101/dolomite#5