[AlbertaGrid] remove support for generic geometries again

AlbertaGrid had experimental support for using the generic geometries
(enabled by a preprocessor macro known to few people).
As we decided on the developer meeting in Aachen to remove the old
generic geometry implementation in favor of the new MultiLinearGeometry,
we need to adapt AlbertaGrid. For performance reasons, we keep the
specialized AlbertaGrid implementation and simply drop the support for the
generic geometry code.
[AlbertaGrid] [cleanup] remove unused traits class

The class AlbertaGridGeometryTraits was only used by the generic
geometry implementation of AlbertaGridGeometry. Since we dropped this
implementation, we can safely remove the traits class.
[AlbertaGrid] [cleanup] remove unused class

The class AlbertaGridCoordStorage was only used by the generic geometry
implementation of AlbertaGridGeometry. Since we dropped the support
for this implementation, we can safely remove this class.
Merge branch 'master' of http://git.dune-project.org/repositories/dune-grid