BERLIN (Reuters) - One in four Germans would be ready to vote in September's federal election for a party that wants to quit the euro, according to an opinion poll published on Monday that highlights German unease over the costs of the euro zone crisis. Germany's mainstream parties remain solidly pro-euro despite grumbling over bailouts of countries such as Greece. A German taboo on nationalism, rooted in atonement for the crimes of the Nazi era, has helped to muffle eurosceptic voices. ...