Add another responsive tables solution that doesn't hide content

Problem/Motivation

In #1276908: Administrative tables are too wide for smaller screens we added a method for resizing tables for smaller screens that hides columns. This works until you get to a point where you have no more 'non-essential' columns to hide. The number of essential columns can vary .

Proposed resolution

I'm not dead set on a solution for I am a fan of the solution we came up with for Responsive Bluecheese: #2225355: Make tables responsive. It uses minimal Javascript and some clever CSS. And we don't need to worry about IE8 any more :-)

Remaining tasks

1. Agree a solution
2. Write the code
3. Identify a good use case in core to use this solution
4. Test

User interface changes

Nicer tables on small screens

API changes

No