improve doc at headers of FullyConnected class
improve doc at headers of FullyConnected class

brunoro/clnn,brunoro/clnn,brunoro/clnn,szagoruyko/clnn,hughperkins/clnn,szagoruyko/clnn,brunoro/clnn,szagoruyko/clnn,hughperkins/clnn,hughperkins/clnn,hughperkins/clnn,szagoruyko/clnn