DEDHAM – The haggard-looking former Hull High School principal who was set to do a stint this summer as a camp swim instructor was ordered held on $10,000 cash bail this morning after authorities say they found thousands of images of child pornography on his computer. Russell Goyette, 61, a longtime teacher who retired as Hull High principal in 2005, pleaded not guilty this morning to 16 counts of possession of child pornography. Prosecutors say a search of Goyette’s personal computer netted more than 4,500 images of children engaged in sex acts with adults and other children. He was indicted...