For Conor McGregor, Boston is somewhat of a home away from home. The Irish UFC fighter will make his boxing debut Saturday in a mega-fight against the undefeated Floyd Mayweather, Jr. at T-Mobile Arena in Las Vegas. And people in the Boston area most certainly will be filling up the numerous Irish bars around the Hub to cheer for McGregor. Boston is an ethnically diverse city, but since immigrants from Ireland began arriving in the 19th century, people of Irish descent have remained its largest ethnic group. McGregor gained their support when he beat Max Holloway at UFC Fight Night Boston in 2013, and it only grew in 2015 when he returned to