Mumbai, April 17 -- A flurry of activity in unlisted NSE shares has nearly tripled the investor base of India's largest stock exchange since it expedited the process of transferring shares between counterparties on 24 March, according to a regulatory circular. The easing is a precursor to a listing of the stock exchange. NSE applied for a no-objection certificate for its IPO with Sebi last August and is still awaiting approval....