Add options for longform display

When placing assets in-line in Longform displays — particularly image and video assets — it would be nice if the "Inline display options" could be a little more robust. Right now for horizontal photos, the "default" and "full" widths display at the same size. Ideally, the "default" width would display images & video assets at 945px wide, and the "full" width option would display them at 1,140px wide (the same width that images display when the images asset is set to "Showcase". 

It would also be cool to have an option to "tile" images side by side, for instance have 2, 3 or 4 images display all in a single horizontal row across the 1,140 display area, and have their individual captions display beneath each image.

These options would give us more robust display options for long-form articles.