By Dhara Ranasinghe and Yoruk Bahceli LONDON (Reuters) – When euro zone interest rates turned negative in 2014, fixed income specialist Michael Hampden-Turner recalls having to explain to baffled bond investors how they could be charged to lend money to governments. As central banks sought to help economies through a succession of crises by making it costly to hoard cash rather than put it to work, investors soon found themselves paying many countries – and even some companies – to take their money. Savers complained that up-ending the practice of charging borrowers interest robbed them of wea…