'a.b.c.d';
Merge pull request #645 from wenshao/master

'a.b.c.d';
xxx
Merge pull request #646 from wenshao/master

xxx
解决PagerUtils.limit 不支持PostgreSQL的bug

参考MySQL的Limit实现，增加PGLimit实现PagerUtils.limit 支持生成PostgreSQL的分页查询sql语句
Merge pull request #649 from lizongbo/master

解决PagerUtils.limit 不支持PostgreSQL的bug
Merge pull request #2 from alibaba/master

merge