Update location (sent and received) for "City" letters

[kmcmullen]

Laura pointed out that for letters in which the address only lists "City" as the location, we are encoding the location in the "deliveredTo" section but not the "sentBy" section, when it should actually be in both places. "City" indicates that a letter is being sent from and to the same city (i.e. within a single city, most often Cleveland).

Not a huge deal, but something we should update at some point, for consistency.