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

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...

Useful, if you are only interested in the jacobian_apply versions
anyway.

There is way more reasons to interpolate a function into the
solution vector and we cover them with one code path:
* Dirichlet boundary conditions (strong ones)
* Initial conditions for instationary expressions
* Initial guesses for Newton solvers

These might sound completely silly, but they are useful when writing
code generic w.r.t. the number of components

It has single precision support...