DATAJDBC-264 - Fix insert statement for empty parameter list.

When an entity consists only of it's id column, the value list contained a single `:`. This commit fixes this. Original pull request: spring-projects#88.

Author: sunnyone

src/main/java/org/springframework/data/jdbc/core/SqlGenerator.java

@@ -260,7 +260,9 @@ private String createInsertSql(Set<String> additionalColumns) {
 columnNamesForInsert.addAll(additionalColumns);
 
 String tableColumns = String.join(", ", columnNamesForInsert);
-String parameterNames = columnNamesForInsert.stream().collect(Collectors.joining(", :", ":", ""));
+String parameterNames = columnNamesForInsert.stream()//
+.map(n -> String.format(":%s", n))//
+.collect(Collectors.joining(", "));
 
 return String.format(insertTemplate, entity.getTableName(), tableColumns, parameterNames);
 }