QtIFW

Implement mechanism to update the maintenace tool.

Have an option to update the maintenace tool without using
the full installer binary. This can be used as fallback in
case the updater/ package manger won't start anymore.

Change-Id: I36be195203cb0172484d739c9f14a2e073ab7792
Reviewed-on: http://codereview.qt-project.org/5885
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@nokia.com>
Reviewed-by: Tim Jenssen <tim.jenssen@nokia.com>