Doc: Adding qt: Integrate Blackberry section into the normal setup

There's just one difference for adding a Blackberry qt version, that
doesn't require a duplication of everything else to explain.

Change-Id: I097d3b30bc823e47b89efe219dd5447608958ee6
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Tobias Nätterlund <tobias.naetterlund@kdab.com>