新增dialog可屏蔽页面的scroll事件支持

Signed-off-by: hancong03 <121371790@qq.com>
解决多实例编辑器下UI相互影响的BUG

Signed-off-by: hancong03 <121371790@qq.com>
Merge branch 'dev-1.2.6' of github.com:campaign/ueditor into dev-1.2.6