Unset default value of keyProperty.

It causes a problem like #902 and makes it difficult to handle errors in Jdbc3KeyGenerator.

Author: harawata

src/main/java/org/apache/ibatis/annotations/Options.java

@@ -58,7 +58,7 @@ public enum FlushCachePolicy {
 
   boolean useGeneratedKeys() default false;
 
-  String keyProperty() default "id";
+  String keyProperty() default "";
 
   String keyColumn() default "";
 

src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java

@@ -300,7 +300,7 @@ void parseStatement(Method method) {
       boolean useCache = isSelect;
 
       KeyGenerator keyGenerator;
-      String keyProperty = "id";
+      String keyProperty = null;
       String keyColumn = null;
       if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
         // first check for SelectKey annotation - that overrides everything else