The controversial Cape Cod Commission Act, which created a regional planning commission with broad growth-control powers, is now a reality. The act was approved last year by the Massachusetts legislature and ratified by Cape voters in a county-wide vote on March 27. It took effect the same day. The act greatly expands the powers of the Cape Cod Planning and Economic Development Commission. The new Commission consists of appointees from each of Barnstable County's 15 towns, one county commissioner, two members of minority groups, and one gubernatorial appointee (also a minority), who will vote only in the case of ties. Few were surprised that Cape voters ratified the act, even though it will add to property taxes (about $7 or $8 a year to