Cleanup of focus.js:

1. Remove dojo/on dependency.

2. Check for events in capture phase rather than bubbling phase.
This is necessary since focus/blur don't bubble (on spec-obeying browsers),
and is also good for the pointerdown event in case someone calls stopPropagation().

3. Use dpointer so I only have to listen for the pointerdown event.

4. Remove some code about ignoring certain focus events.
This was from https://bugs.dojotoolkit.org/ticket/9735 and dealt with the
onactivate event that we are no longer using.
Get focus.html test working; still needs to be converted to intern.