Fixes #973: 'valuechange' event e.stopPropagation

'valuechange' event now supports e.stopPropagation() and
e.stopImmediatePropagation().
Further 'valuechange' event fixes.

Fix tests according to rgrove's comments.

Consider the condition in which there are two listeners on the same
element and added test for it:
Listener 1 calls e.stopPropagation(),
Listener 2 calls e.stopImmediatePropagation()
Update event-valuechange history.
Build event-valuechange.