By Lefteris Karagiannopoulos ATHENS (Reuters) - They might be living through one of the worst economic crises of modern times, but for Greeks coffee remains an indispensable fuel for thought on the eve of a referendum that may decide their future in Europe. Hit by falling pensions and wages, higher taxes and soaring unemployment, Greeks of all walks of life have cut back on consumption. "Greeks are ready to cut anything else, but not their coffee.