Rewrite of the whole help modul initialization.
We now do as much as possible lazy initialisation, e.g only start the full text search indexer if we really access the search widget. Also moved the QFutur progress into the search widget. Changed all ctors to be called without an argument, since we share the help engines from help manager all over the place. Make use of the fact that we only need to call setupData on the gui engine if we access the help mode, otherwise all data is fetched thru the core engine whichs setupData is really fast.