To properly layout the axes, it is necessary to specify on
which side of the chart they are located.
There is already an "Orientation" enum. However, that gives
the direction (top-to-bottom, etc.), but not the position.
It might become obsolete in the future, since the direction
can also be expressed by setting min and max accordingly.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
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