Enabled keyboard accessibility

Enabled keyboard accessibility by 
1. adding in tabindex=0 to the th elements dynamically so that they can be focussed
2. adding keypress and then ignoring anything that isn't the enter key.

I was unable to work out what the section commented as *// apply easy methods that trigger bound events* did, so haven't added keypress to the unbind list there.  Could you please check if it is required there?