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.
In case of split mode we did not check if the actual requested doc
exists and thus did fail to open the browser if it could not be found.
Reviewed-by: Daniel Molkentin
