HierarchyWidget: wrap text instead of scrollbar

[jusa3]

Provide the option (if possible optional: either wrap or scrollbar) of wrapping the text if the parent component isn't wide enough.

https://semanticlookup.zbmed.de/ontologies/mesh/tab/

[VincentKneip]

On the branch hierarchy-wrap (see linked development branch), I added an optional boolean parameter wrap to the HierarchyWidget, toggling between text wrap and scrollbar. Its default value is false (scrollbar).

A major refactor of the widget CSS was necessary to allow for an aesthetic text wrap. The scrollbar view should be almost as before the refactor.

Here's an impression of the difference in appearance of wrap=true and wrap=false:

scroll (wrap=false)	wrap (wrap=true)