Cannery-Grocer Swap

A simple mod addressing which annoys me more than it really should. Now the Cannery is a Warehouse building boosting Food production and preserving it for transport, possibly from a town to a city, and the Grocer is an urban building distributing Food locally. From a gameplay perspective, there are still the same two buildings. Just their names and visuals are swapped. Let me know if I should adjust the unlock techs though, as now the Cannery is free (I'd maybe move it to Military Science) whereas the Grocer now requires Mass Production to unlock (I'd maybe move it to Urbanization).