Dan Rather, one of the giants of American broadcast journalism, is to leave the channel he has worked at for 44 years, for a position at a little watched cable channel. CBS announced yesterday that Rather, 74, would be leaving the channel where he hosted the evening news for 24 years until he stood down last year. --Snip-- Rather has said in recent days that he was unhappy with the new role being offered him at the channel, where he has covered most of the big stories of the past 40 years, from the Kennedy assassination to the invasion of...