LONDON (Reuters) - A focus on fewer diseases, together with cuts in laboratories and staff, has delivered a more than fourfold increase in research productivity at drugmaker AstraZeneca , based on one key measure of success. The analysis published on Friday comes at a time of soul-searching among large pharmaceutical companies as they compete with smaller biotech firms, which are getting new drugs to market more efficiently. The turnaround evident this decade at AstraZeneca fo