European pay TV giant Sky, controlled by 21st Century Fox, has invested $10 million in DataXu, a Boston based provider of marketing analytics and data management software for programmatic advertising. The aims is to boost reach and accelerate take up, of its emerging AdVance cross platform advertising system. Sky says the move also fits its strategy of investing in companies which provide core elements of its technology, to get more closely involved in development, while at the same time looking for long term financial gains. It follows a variety of other such investments, including $4 million in software encoding vendor Elemental Technologies, as well as OTT video company TV4 Entertainment, online video aggregator Pluto TV, online sports network Whistle Sports,…