Very annoyingly, to render the profile for printing / export,
the profile still had to be show()n, thus requiring a parent
window.
Analysis of qmlprofile.c showed that this was due to the
transformation matrix not being properly set up on non-show()n
scenes.
Instead, we can simply render via the QGraphicsScene
(circumventing the QGraphicsView).
The code was factored out into the ProfileWidget2::draw()
function. This will hopefully make it easier to change
the size-code of the profile.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>