Reviewed-by: kh1

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.

The check should be done in the semantic phase.

Reviewed-by: Thorbjorn

There's an issue with receiving the release event when the mouse is
moved slightly, and also on Linux it is apparently normal to handle
these events on press instead of release. Tested with Firefox and
Chromium.

Task-number: QTCREATORBUG-899
Reviewed-by: kh1