Nikkei falls to 3-week low on profit-taking, soft tankan survey

* Japanese investors take profits on first day of 2015/16 * BOJ's tankan softer than expected * Drugmakers and other recent gainers hit hardest By Hideyuki Sano TOKYO, April 1 (Reuters) - Tokyo shares fell on Wednesday as investors sold recent gainers to lock in profit on the first day of Japanese financial year and after soft reading on the Bank of Japan's tankan business sentiment survey. Both the Nikkei share average and the Topix fell below their 25-day moving average, a