Import the QtWebKit documentation

This places the documentation in separates .qdoc files with the original
license header preserved. We don't want to contaminate our implementation yet
just for the documentation, so keep it separate for now.

New documentation that isn't attached to the QtWebKit LGPL license should go
inline in the code as usual.

Change-Id: I113a9ad2b826ed7cea053be065f201b637070d28
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Rough port of the documentation to QtWebEngine

This is a gross mechanical modification of the documentation, along with build
system bindings to allow it to generate. This should allow doing iterative
improvements to the documentation from now on.

This fixes project-related qdoc warnings but we still need to do some serious
work to get the documentation better fitting QtWebEngine. All the documentation
is ported to match the current state of our headers (without trying to adapt
to modified APIs yet) and we should clear the part of the documentation that we
don't need at the same time that we clean up our public headers.

Change-Id: I6fb4e10e8b4c1c53be7bc7c581286248ac04d4da
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Do not store a WebContentsAdapter directly in QWebEngineHistory

The adapter might change, while the page association should
always remain.

Change-Id: Ib2b49c599d497864484dd6758f47473d70fe4cb3
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Implement QWebEngineHistory serialization

This does uses logic taken from Chromium's state save and restore
code. The history version is incremented from the same method in
QtWebKit in cases where the application would try loading a stream
from a previous version using QtWebKit.

In all cases where Chromium does a restore of a serialized history,
it does so on a fresh WebContents instance, thus we must do the same
and some of the initialization code has to be updated.

Change-Id: I45abb052073bd44c9cb47bc2abcf4b558fe3dbbd
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Fix tst_QWebEngineHistory::clear()

Make sure that the navigation actions are updated when clearing the history.

Change-Id: I663d2b68164dd695005165595ea08d051aae9fab
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Implement QWebEngineHistoryItem::lastVisited

Change-Id: I105cb2a0a2479b146e2ab68db6d194ac2ac2d3f9
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>