SEASON PREMIERE: Next year it will be 20 years since NBC premiered JAG, a drama about lawyers working in the Navy. NBC canceled that show after one season, but CBS picked it up, and watched it develop into a hit series that ran for a decade. And in the interim, in 2003, CBS launched a spinoff series, called NCIS, which now is the most popular drama series on television, and has launched several spinoffs of its own. (Basically, NCIS is to NBC what The Beatles are to Pete Best.) And tonight, on the same evening NCIS launches its latest spinoff, NCIS: New Orleans, it also presents the season premiere of its own series. Season premiere number 12.