ALBANY — Gov. Andrew M. Cuomo signed into law on Tuesday a sweeping package of gun control measures, significantly expanding a ban on assault weapons and making New York the first state to change its laws in response to the mass shooting at a Connecticut elementary school. Mr. Cuomo signed the bill less than an hour after the State Assembly approved the legislation on a 104-to-43 vote. The State Senate approved the measure, 43 to 18, on Monday night. The expanded ban on assault weapons broadens the definition of such weapons, banning semiautomatic pistols and rifles with detachable magazines and...