Hilton just launched Undergraduate Hotels—the hospitality giant's 28th brand. A rendering of the front desk at the Undergraduate by Hilton.Credit: HiltonHilton already had 27 brands. Number 28 is for the next time you're stuck in a college town with nowhere decent to stay.The company’s latest move is the launch of Undergraduate, a new lifestyle brand (yes, another) that brings school-spirit design and a serious bar program to university towns.“L…