By Karen Brettell Dec 17 (Reuters) - The recent crypto market bust has left some investors more cautious, after hitting some of the hottest and most-hyped corners of the industry the hardest. It may also provide a boon to emerging strategies that seek to more actively manage risks. The universe of crypto investment alternatives has expanded dramatically in just a ​few years and now includes direct cryptocurrency purchases, spot ETFs, derivatives like put and call options and futures, shares in mining and ...