By Daniel Kline The fast-good giant plans a summer full of deals, secret menu items moving to the regular menu, concerts, and limited-edition gear (like a retro Grimace pool float) A lot of fast-food chains have a secret menu but some are more secret than others. Starbucks (SBUX) – Get Starbucks Corporation Report, for example, has a lot of secret menu items that have become pretty commonly known and a few which have even crossed over to the regular menu. This type of secret menu has its positives and its negatives for a chain. On the positive side, having a well-known “secret” makes people fe…