When it comes to the Rolling Stones, you can put aside all the jokes about age and senior citizenship, about walkers and hip replacements. Yes, they’ve been a band for 53 years. Yes, the four members are a combined 284 years old. And, yes, their lead singer is a great-grandfather. But Saturday night at Arrowhead Stadium, the Stones proved demonstrably that rock and roll is more about spirit than age and they can still be as fierce as any rock band on earth.