JDK9 compatibility: replace DatatypeConverter with Base64 (#999)

Author: valfirst

src/main/java/io/appium/java_client/InteractsWithFiles.java

@@ -23,7 +23,8 @@
 
 import org.openqa.selenium.remote.Response;
 
-import javax.xml.bind.DatatypeConverter;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
 
 public interface InteractsWithFiles extends ExecutesMethod {
 
@@ -50,7 +51,7 @@ default byte[] pullFile(String remotePath) {
         Response response = execute(PULL_FILE, ImmutableMap.of("path", remotePath));
         String base64String = response.getValue().toString();
 
-        return DatatypeConverter.parseBase64Binary(base64String);
+        return Base64.getDecoder().decode(base64String.getBytes(StandardCharsets.UTF_8));
     }
 
     /**
@@ -76,7 +77,7 @@ default byte[] pullFolder(String remotePath) {
         Response response = execute(PULL_FOLDER, ImmutableMap.of("path", remotePath));
         String base64String = response.getValue().toString();
 
-        return DatatypeConverter.parseBase64Binary(base64String);
+        return Base64.getDecoder().decode(base64String.getBytes(StandardCharsets.UTF_8));
     }
 
 }