Scaladoc display on completion & showToolTip

integrated with completion and 'Show tooltip'/F2 (which is not exactly hovers)
pinging @sschaef  because he should see the ugly handover from `getHoverInfo2` to `getHoverInfo`
<< I'm open for ideas on how to improve it which do not imply rewriting the `HtmlProducer` in `Scaladoc`
BrowserControlCreator shouldn't be needed. `new HoverControlCreator(new FocusedControlCreator(ScalaHover.HoverFontId), ScalaHover.HoverFontId)` does the same, but `FocusedControlCreator` creates a toolbar, which is probably not needed in completions (but can easily disabled by disabling the creation of `ToolBarManager` in `FocusControlCreator`).