JDBC batch updates

Add support for JDBC batch updates. It includes an implementation of
Statement.*Batch(...) as well as PreparedStatement.*Batch() methods.

Under the hood SQLConnection uses the pipelining sending requests one by
one asynchronously and awaiting all of them. There are some issues
regarding vinyl storage engine where execution order are not specified
and DDL statements which are not transactional.

Closes: #62

Author: nicktorwald

src/main/java/org/tarantool/jdbc/SQLStatement.java

@@ -17,6 +17,8 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.stream.Collectors;
@@ -44,6 +46,8 @@ public class SQLStatement implements TarantoolStatement {
 
     private List<String> batchQueries = new ArrayList<>();
 
+    private List<String> batchQueries = new ArrayList<>();
+
     private boolean isCloseOnCompletion;
 
     private final int resultSetType;