Implement basic editing actions for QWebEnginePage

Change-Id: I1b58d2b2e86f60e296ae48095ed8d5e8172e0d1e
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Fix the Mac build with a -no-framework Qt

If QMAKE_FRAMEWORKPATH is empty, this would add an empty entry to the list
and would end up with a -F with no argument added to the clang command line.

This would fail the build since the next switch would be eaten by the -F.

Change-Id: I42657e781278fd56d6664a42fb4222eb83b3cd73
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Fix a crash when using the history on an adopted page

We also need to update the WebContentsAdapter pointer in
QWebEngineHistoryPrivate.

Change-Id: I8251e9834b179747b6b65630cf4ced5c2b1af27f
Reviewed-by: Andras Becsi <andras.becsi@digia.com>