Boston’s Department of Public Health is unveiling changes to the way it issues licenses under the state’s medical marijuana dispensary program. The changes outlined in mid-May include a revamped application process that allows marijuana dispensaries to be approved similar to how other healthcare facilities, such as pharmacies, are licensed. Under the new process, dispensaries will be evaluated individually, not as part of a group. The state has issued only three certificates of registration, and, to date, no dispensaries have opened.