Remove inline onclick, replace with a module

* Avoid using the javascript onclick attribute
* Create a re-usable module that can be applied to any mousetrap key
combination and link

cc @issyl0
Tidy up jump to mapping modal and link

* Alter opening strap-line of app to be more helpful to new users, by
providing instructions rather than stats
* Keep the stats available in column headers
* Add a footer to the modal