QtIFW

Support to Operations for method execution from main thread

 - Operations can request invocation of an arbitrary method which will be executed from the main thread
 by emitting requestBlockingExecution(const QString &invokableMethodName)
 The operation will block until the call returns.

Change-Id: If03ce2b7d7989eeb543d3902965f61dd7ab03749
Reviewed-on: http://codereview.qt-project.org/5698
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Tim Jenssen <tim.jenssen@nokia.com>