Extend keymaster to support dispatching key events to elements

 You may not care for this direction, but FYI.

Extend keymaster to support dispatching key events to elements. 
Overload key() to include key(descriptor, view, element) 
where |descriptor| is the same as the shortcut definition version, 
|view| is the dispatch view (defaults to 'window'), 
|element| is the dispatch target.

Add selftest.html, modified from test.html to issue console.warn
for passing tests and console.error for failures.

Tests pass but I've not driven this model out on the road yet.