Now we can select multiple notes. API - Changes:

### Implementation changed by maintaining backwards compatibility

* rangeHightlight(start, end)

### new API

* rangeHighlightMore(start, end)
* rangeUnhighligtMore(start, end)

maybe the following ones could be made private

* highlightElements(elements) - elements result of getElementsByRange(start, end)
* unhighlightElements(elements) - elements result of getElementsByRange(start, end)
* getElementsByRange(start, end) - yield an array of drawn objects for highlightElements / unhighlightElements