TOKYO, Nov 19 (Reuters) - The Nikkei average is expected to open higher on Monday on growing expectations that Japan's main opposition party will win next month's election and increase pressure on the central bank to ease monetary policy. A call by Liberal Democratic Party (LDP) leader Shinzo Abe for the Bank of Japan to further stimulate the ailing economy, including setting interest rates to zero or below zero, has weakened the yen and boosted the shares of Japanese exporters. The yen