Add a framework probe.

Change-Id: Ifa968ca9eef1e4eb0b0d6b08872199172cc7b5df
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Use the new sub-project feature in the qbs project files.

Change-Id: Ia30766b91ef28d05bc1f6109d6dedbb7d18bcf3d
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>