making the erb_gen script flexible to handle predefined cache lifespan and cache age if provided for a layer.
making the erb_gen script flexible to handle predefined cache lifespan and cache age if provided for a layer.

mapzen/vector-datasource,adncentral/vector-datasource,zoondka/vector-datasource,mapzen/vector-datasource,adncentral/vector-datasource,gronke/vector-datasource,adncentral/vector-datasource,zoondka/vector-datasource,gronke/vector-datasource,mapzen/vector-datasource,kyroskoh/vector-datasource,adncentral/vector-datasource,kyroskoh/vector-datasource