Merge branch 'master' of https://github.com/wwu-numerik/dune-stuff

Conflicts (resolved to remote branch):
	dune/stuff/fem/customprojection.hh
	dune/stuff/fem/error.hh
	dune/stuff/fem/functionadapter.hh
	dune/stuff/fem/functions/checks.hh
	dune/stuff/fem/functions/integrals.hh
	dune/stuff/fem/functions/magnitude.hh
	dune/stuff/fem/functions/timefunction.hh
	dune/stuff/fem/localmatrix_proxy.hh
	dune/stuff/fem/restrict_prolong.hh