FRANKFURT (Reuters) - It was meant to be a fleeting slowdown for Europe's economic powerhouse, followed by a rapid rebound. Instead, Germany has been stuck in neutral for a year with hopes fading for a turnaround, a situation that threatens to spread lasting economic gloom across Europe.Its vast industry is in recession, a victim of shifting consumer trends, China's economic rebalancing, and a global trade war. Investment spending is shrinking, sentiment is souring, job creation has stalled and..