The North Penn School Board has unanimously approved a new contract with its chief administrator.   Superintendent Curt Dietrich will serve in the leadership post for an additional five years.   He earns about $201,000 annually.   District officials say he was due an increase for the current school year as well as the last one but turned down both.   Doctor Dietrich has been at the helm of the district for about two-and-a-half years.