Take Five: Bear-y Christmas! World markets themes for the week ahead

(Reuters) - Following are five big themes likely to dominate thinking of investors and traders in the coming week and the Reuters stories related to them.1/CHAOS FOR CHRISTMASDonald Trump's U.S. presidency has lurched from crisis to crisis since he took office, but turbulence is reaching new highs just in time for Christmas.The resignation of Defense Secretary James Mattis after a major reshaping of the superpower's global military footprint has grabbed headlines, coming on the heels of other..