Deprecate the methods leafView and levelView without template parameter

Because they have been renamed to leafGridView and levelGridView, respectively.
Deprecating the corresponding methods with the PartitionType template parameter
currently exceeds my C++ skills.
(cherry picked from commit d705c4a98de5f17a4a94cf06690a4e1d8660ab87)

Conflicts:
	dune/grid/common/grid.hh
properly deprecate methods leafView and levelView

Only the non-template versions of leafView and levelView have been
deprecated, yet. This patch also deprecates the template versions as
described in the documentation of <dune/common/deprecated.hh>.
(cherry picked from commit 06090e3307837f2fea97f81d2fdced816c263634)

Resolved conflicts:
	dune/grid/common/grid.hh