replace .visible-{size} with .visible-{size}-{display}

Adds `.visible-{screen size}-block`, `.visible-{screen size}-inline`, and `.visible-{screen size}-inline-block` classes (and also a corresponding trio for `.visible-print`). Also deprecates the `.visible-{screen size}` classes.

Proposed fix for #8869 pursuant to #9397. Includes docs updates.

There is most likely a way to refactor this to be less repetitive & more concise by using some more sophisticated Less features, but this should be okay for the time being.

/to @mdo for review.