改进Db\Driver类
增加快捷调用方式 cache(10) 等同于 cache(true, 10)
改进think_filter函数
Merge branch 'master' of https://git.oschina.net/liu21st/thinkphp
Merge branch 'master' of https://git.oschina.net/liu21st/thinkphp
Merge remote-tracking branch 'origin/master' into wilsonjnliu/master