ATHENS (Reuters) - Greece's conservative leader pushed on Monday for a new coalition government after a narrow election victory, pledging to soften the debt-laden country's punishing austerity program despite opposition from Germany. A brief relief rally on international financial markets after Sunday's Greek vote quickly fizzled out as it became clear that Antonis Samaras's New Democracy had failed to win a convincing popular mandate to implement the deep spending cuts and tax increases demanded by the European Union and the IMF. ...