add template paramter for coordinate type

dune/foamgrid/dgffoam.cc

dune/foamgrid/dgffoam.hh

dune/foamgrid/foamgrid.hh

dune/foamgrid/foamgrid/foamgrid.cc

dune/foamgrid/foamgrid/foamgridedge.hh

dune/foamgrid/foamgrid/foamgridelements.hh

dune/foamgrid/foamgrid/foamgridentity.hh

dune/foamgrid/foamgrid/foamgridentitypointer.hh

dune/foamgrid/foamgrid/foamgridentityseed.hh

dune/foamgrid/foamgrid/foamgridfactory.hh

dune/foamgrid/foamgrid/foamgridhierarchiciterator.hh

dune/foamgrid/foamgrid/foamgridindexsets.hh

dune/foamgrid/foamgrid/foamgridintersectioniterators.hh

dune/foamgrid/foamgrid/foamgridintersections.hh

dune/foamgrid/foamgrid/foamgridleafiterator.hh

dune/foamgrid/foamgrid/foamgridleveliterator.hh

dune/foamgrid/foamgrid/foamgridnulliteratorfactory.hh

dune/foamgrid/foamgrid/foamgridvertex.hh