So far, it did not set the qp tuple correctly and
thus sometimes resulted in too big numbers being
chosen.

This reverts commit 5081753a.

In that case you need two GridFunctions, which can be
bound to the two cells.

Needs monkey patching of the preprocessing to not
transfer to reference element...

After consulting Steffen

It makes the code generation workflow more complicated without
contributing anything substantial

Instationary stuff not fixed so far.

The previous name was *really* confusing.

Much more telling name...