A state grant to support the extension of a rail road line in Milton is expected to promote economic development.  A Transportation Economic Assistance grant will help build a rail extension to the new Clasen Quality Chocolate factory.  Milton City Administrator Al Hulick says new rail lines are extremely rare in southern Wisconsin, and the new line could be used by other industry in the community, as well as Clasen.   He says Clasen will actually pay the bulk of building the line, and then turn ownership over to the city.  Clasen Quality Chocolate hopes to begin production by the fall of next year.