All hail the end of summer! And even if it is still 90° outside, witness the harbingers of fall. The conventions are at last over, the election campaign is on, the summer reruns are depleted, and the new TV season is about to begin. As for the conventions, the Republicans won the dullness contest by acclamation. The party of the “Great Communicator” was not up to its usual standards in speech making. Its keynote, from Treasurer Angela Buchanan, was the worst in memory, delivered in a style reminiscent of Romper Room. The Republicans also carried on two unflattering national habits seen on the Olympics: chanting “U! S! A!” like nationalistic graduates of Animal House and booing at every mention of the Democrats in President Reagan’s speech. For their part, the Democrats had filled their few hours on the tube with petty squabbling; that doesn’t win elections, but it did make for more entertaining TV. At least both shows—The Democrats of Hazzard and Little White House on the Prairie—provided a break from reruns and failed pilots. The networks have overruled Mother Nature and declared that the fall season will start early this year—next week to be exact. So this week we tie up some summer-season odds and ends: one failed pilot, one good but not-ready-for-sweeps-weeks special and a look at the worst show on daytime TV.