The wait’s finally over. Lakers’ media day, marking the start of training camp, is today. That means Lakers fans will finally have something substantive to talk about regarding the 2012-13 season. Below are the top five storylines as Lakers’ training camp opens on Tuesday. 1. How will Dwight Howard’s back rehab go? The Lakers don’t expect this to be a long-term issue. They’ve reported no setbacks on his surgically repaired back. And indicative of his on-court workouts last week and a bit of dancing on “Ellen,” it appears Howard has come a long way since going under the knife five months ago. Still, Laker fans never like to wait. They want to see Superman officially wear a Lakers uniform. They want to get a glimpse of how his towering presence will immediately upgrade the defense. They want to see how his pick-and-roll mastery with Steve Nash will enhance the offense’s productivity. For fans who will only see the Lakers in person during exhibition games, the urgency bodes even higher. Nonetheless, Howard and the Lakers maintain …