Curtis Jackson (aka 50 Cent) catapulted to fame with the release of his 2003 album “Get Rich or Die Trying.” Movies, philanthropic endeavors, and high-profile collaborations soon followed. But before he was a household name, 50 Cent held a far less favorable title than “recording artist.” He was, by his own admission, a “neighborhood bully.” But this week, he hopes to mend some of his past with his new young adult novel “Playground.” Unlike most bullying books and conversations out there, it looks at bullying from the point of view of the bully.