[dune-fem] Direct sum of spaces

[Agnese, Marco]

Hi Martin,

> But given the tools in the tuple space you can easily write such a space. The 
> only difference between the tuple space and your desired space is the 
> basisfunctionset. You simply want it to sum the basis functions instead of 
> multiplying them by e_i (where i is the position in the tuple) This can easily 
> be adapted (in a copy, of course). Unfortunately, I cannot space you to write a 
> big lot of boiler-plate code. Maybe others would also be interested in such a space.

yes this was exactly what I was asking. Since nothing is already implemented, I will try to implement it and I will add to dune-fem as soon as it works.

Cheers,
Marco.