Don't install into sysroot by default.

Task-number: QBS-249

Change-Id: I8c4dd985873afd48f65dbc1e368a52b4acadc9c2
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
fix error message for referenced non-product items

Change-Id: Iba007b7d6c611f71512c8925ef968b71ced0889e
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>