QtIFW

Use QSet throughout the whole code, saves us QList conversions.

Remove default parameter from Repo ctor, lead already to confusion.
Also add some more specific {get/set} repo functions, to be able to
distinguish between the different kind of repositories (needed for
setting dialog).

Change-Id: I2c1e4d5377799f54e408a89785bdc5f01619f846
Reviewed-by: Tim Jenssen <tim.jenssen@nokia.com>
Reviewed-by: Alexander Lenhardt <alexander.lenhardt@nokia.com>