Depending on your sentimentalities for the agrarian age, today may be a sad day. The last-known operating farm inside the Beltway has been sold off and being prepped for a Giant supermarket and strip mall. Duane Dickerson, who has grown tired of defending his Prince George’s County farm from increasing crime in the county, decided enough was enough and sold it to a North Carolina-based developer, the AP via WTOP reports. But Prince George’s County…