Add static method to extract generatorSignature from block reference

src/main/java/org/qora/transform/block/BlockTransformer.java

@@ -277,8 +277,12 @@ public class BlockTransformer extends Transformer {
 		}
 	}
 
+	public static byte[] getReferenceGeneratorSignature(byte[] blockReference) {
+		return Arrays.copyOf(blockReference, GENERATOR_SIGNATURE_LENGTH);
+	}
+
 	public static byte[] getBytesForGeneratorSignature(BlockData blockData) throws TransformationException {
-		byte[] generatorSignature = Arrays.copyOf(blockData.getReference(), GENERATOR_SIGNATURE_LENGTH);
+		byte[] generatorSignature = getReferenceGeneratorSignature(blockData.getReference());
 		PublicKeyAccount generator = new PublicKeyAccount(null, blockData.getGeneratorPublicKey());
 
 		return getBytesForGeneratorSignature(generatorSignature, blockData.getGeneratingBalance(), generator);