Reviewed-by: ck

If a plugin requests asyncronous shutdown, the shutdown sequence does
not continue to deleting the plugins before it has sent a
asynchronousShutdownFinished signal. During that time an event loop
is running.

Task-number: QTCREATORBUG-1765
Reviewed-by: ck

If we where not in full help mode at least once, the engine
would still run without valid help collection due to the new
lazy initialisation, thus the right side pane would not be
able to retrieve the requested help file.

Reviewed-by: ck

If we where not in full help mode at least once, the engine
would still run without valid help collection due to the new
lazy initialisation, thus the right side pane would not be
able to retrieve the requested help file.

Reviewed-by: ck

A mostly mechanical change.

Reviewed-By: con

Reviewed-by: ck

Reviewed-by: ck

 - lessens open file handles
 - improves help plugin startup further

Task-number: QTCREATORBUG-337
Reviewed-by: ck

Reviewed-by: Leena Miettinen

Reviewed-by: ossi

When changing the language, the sidebar items would break because
their localized window titles were used for storing the settings. Now,
id's are used.

Reviewed-by: con

Discussed-with: hjk

* Make sure we only change our own urls inside that function
* QDesktopService::setUrlHandler expects the target slot to take a QUrl

Reviewed-by: ck

Also put it at the top, since it looks better there with the icon.

Reviewed-by: ck

Font stuff is now handled completely inside the help viewer class.

Reviewed-by: ck

To make the addition of the qml docs more prominent, make the content
item the default one as it shows all available documentation sets.

Task-number: QTCREATORBUG-1024
Reviewed-by: kkoehne

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.

Currently we can only retrieve a list of keywords from the help index
model, which is slow and needs a fully setup gui help engine. This needs
to be implmeneted in the help lib though.

Reuse the core help engine in the settings pages. Do not setup the gui
help engine at all since any getter will do so. Split update documentation
into smaller pieces for better performance.

Reviewed-by: ck

Reviewed-by: ck

Reviewed-by: ck

Reviewed-by: ck

Reviewed-by: kh1

We need to append "?view=split"to force the split mode check. Make the
check more readable in viewerForContextMode.

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