odds and ends: adding activateNode test stubs; add setCursor (untested); some cleanup
fixing the focusFieldVal bug: 1) triggering ContentField.focus instead of NodeItem.focus; 2) limit the selector to trigger on '> .content-field' instead of ALL .content-fields; 3) focus callback to use stopPropagation instead of return false;
also adding a call to dc.unfocus before dcnext/prevNode (so that focus isn't retained on a literal-node's content field when moving to a non literal node)
also adding wrapping dc.commitChange's replaceWithJson in Ember.run so that the modifications to the underlying nodes occur (and the corresponding views are inserted) before other UI modifications (focusing in on the contentfield)