ZURICH (Reuters) - UBS has reorganised its pay policy for 10,000 back-office workers, Switzerland's biggest lender said on Monday, changing how their bonuses are calculated.The staff -- mainly working in functions like human resources, marketing and communication -- will have their bonuses shifted from a variable scheme to a fixed percentage of their salary.The move aimed to reduce uncertainty around compensation rather than to scale back the amount paid, the bank said."While not guaranteed,..