East Baltimore’s Johnston Square neighborhood has long been hailed by local government leaders as an example of how the city can turn its surplus of vacant homes around. Once badly blighted and devoid of new investment, the community saw many of its homes — and its lifeblood — go dark over the years. But over the last decade, vacancy rates there have fallen, homeowners have moved in and neighbors say property values have increased. Developer ReBUILD Metro is reviving the neighborhood whole block