Slim elements on facia-press

Start slimming down the size of the `elements` key for each piece of content in the `pressed.json` files. This dramatically decreases the size of the file.

For example; `/uk` on `DEV` for me was coming out at around `5.3MB`, it is now `1.8MB`.
`/au/culture` went from `4.2MB` to `1MB`.

This simply emulates how the templates get elements from pieces of `content`; using `trailPicture(5, 3)` and also using `ElementsProfile.elementFor` to take the largest `Asset`.

@robertberry @stephanfowler