base

in the browser, make the trackball more like a mouse

Older code treated the trackball as a four way dpad with
equivalents to moving up, down, left and right by generating
arrow key events. This change makes the trackball solely
generate mousemove events.

The old arrow keys in turn were mapped to be as close as
possible to tab-key events that moved the focus. The new
model leaves focus-changes to the DOM.

Clicking the dpad is distinguished from pressing the enter
key to be more compatible with desktop-authored web pages.