Added Doxygen documentation.
But: I cannot find the right doxygen settings to create macro documentation!

Conflicts:
	dune/stuff/function/expression.hh
	dune/stuff/grid/provider/gmsh.hh
	dune/stuff/grid/provider/interface.hh
	examples/grid/providers.cc

This reverts commit 8b201f5ee86fa08202ea9410f290562a46ff7eec because it was an anti-fix.

you can now use HAS_STD_BEGIN_END and HAS_LAMBDA_FUNCTIONS to wrap code

because we should be able to handle dune-fem 1.3^^

This reverts commit 1506cc6360c63591626658ff4198b3fefc3ce65b.

Conflicts:

	.gitignore

Reverted because configure does not succeed anymore:
...
configure: creating ./config.status
config.status: creating Makefile
config.status: creating dune/Makefile
config.status: creating dune/stuff/Makefile
config.status: creating dune/stuff/common/Makefile
config.status: creating dune/stuff/fem/Makefile
config.status: creating dune/stuff/fem/functions/Makefile
config.status: creating dune/stuff/function/Makefile
config.status: creating dune/stuff/grid/Makefile
config.status: creating dune/stuff/grid/provider/Makefile
config.status: creating dune/stuff/grid/output/Makefile
config.status: creating dune/stuff/projection/Makefile
config.status: creating dune/stuff/test/Makefile
config.status: error: cannot find input file: `dune/stuff/test/gtest/Makefile.in'
...