QtIFW

Expose some private functions and make use of it.

It should be way faster to iterate over the known installed
packages list instead of all components to figure out if they
are installed.

Change-Id: I2fdb54c4063a3a886828129ad344c59216eb6509
Reviewed-on: http://codereview.qt.nokia.com/3173
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Niels Weber <niels.2.weber@nokia.com>
Reviewed-by: Tim Jenssen <tim.jenssen@nokia.com>