Craig Wallace and Jeff Allin in Round House Theatre’s production of ‘Permanent Collection’. Photo by Danisha Crosby “You can’t be on both sides.” So says Sterling North (Craig Wallace), the new director of a private suburban art museum in Thomas Gibbons’ trenchant, provocative Permanent Collection. Sterling knows exactly which side he’s on, and so does his opposition, the museum’s education director Paul Barrow (Jeff Allin). The two are so far into their respective sides…