*  mln/kernel/aggregate/inf.hpp: Add inf kernel aggregate.
	*  mln/kernel/function.hpp: Add function meta term.
	*  mln/morpho/erode.hpp: New.
	*  mln/morpho/gradient.hpp: New.
	*  tests/morpho/CMakeLists.txt: Update.
	*  tests/morpho/gradient.cpp: New.