Qt Quick app wizard: Merge two .pri files into one

As an project tree unclutter measure, we now append the
deployment.pri to the qmlapplicationviewer.pri while generating
the stub for Qt Quick Apps.

At the same tame we keep te Qt Mobile App wizard intact, which
continues to generate the deployment.pri file.

And we also keep the qmlapp/app.pro template functioning as
project, therefore we leave the include(../shared/deployment.pri)
in qmlapp/app.pro and let the wizard remove that incude.

Task-Number: QTCREATORBUG-2568
Reviewed-By: ck