A team of teenagers is tasked with saving the planet in “Power Rangers.” (Kimberly French/Lionsgate via AP) By M. Scott Morris Daily Journal Up to a point, the new movie, “Power Rangers,” has a lot in common with an after-school special. A bunch of misfits are thrown together and learn they’re not so alone after all. And then they transform into brightly colored warriors and battle an ancient scourge (Elizabeth Banks) and the glistening metal giant she commands. Jason (Dacre Montgomery) does something stupid and gets sent to detention, where he meets Kimberly (Naomi Scott) and Billy (RJ Cyler), who both did their own stupid things and got sent to detention. For different reasons, the three explore a gold mine, where they meet Zack (Ludi Lin) and Trini (Becky G.), and all five find colored medallions that open up a world of possibilities and problems. Anybody with passing knowledge of the “Power Rangers” TV shows knows there’s going to be a bunch of fighting in this movie. But it takes a while to get to the violence.