io/storage: add JSON support

Bincode can't deal with a number of serde's features that would be
desirable if we're using the same Serialize impls for generating JSON
data for the viewer.

src/core/region_processor.rs

@@ -148,6 +148,7 @@ impl<'a> SingleRegionProcessor<'a> {
 		storage::write_file(
 			&self.output_path,
 			&self.processed_region,
+			storage::Format::Bincode,
 			REGION_FILE_META_VERSION,
 			self.input_timestamp,
 		)