[la.container.eigen] fixed 4beb48913766058fc6c6bcf45591371c4a6c3aed

There were several errors related to the recent split of the eigen backend
which are hopefully fixed now.
[la.container...interfaces] give default for ScalarType

This allos the interfaces to be used as they were before.
[cmake] silence dune-fem warning w/o alugrid present
[common] adds -Wundef to gcc branch in disable_warnings.hh
[grid] removes deprecated ConstDefault ctors
[grid] gets rid of unused param warnings in gridfactory
Merge branch 'master' into less_shared_ptr