[Dune] alugrid 1.1 as a strict requirement

[Christian Engwer]

Dear Robert, dear rest,

I have a small question regarding the new requirement for alugrid
1.1. I tried to compile my latest dune with the not so latest alugrid
1.0 lib and test work fine.

Is this really a hard requirement?

Especially for the 1.0.1 branch I would suggest to keep the
requirements as low as possible. We decided to release with exactly
the feature set dune had during the meeting in Berlin and only
incorporate the most important bugfixes.

Thanks
  Christian