adding common-questions doc page
adding common-questions doc page

druud62/gh-ost,druud62/gh-ost,shuhaowu/gh-ost,shuhaowu/gh-ost,groenewold-pythian/gh-ost,groenewold-pythian/gh-ost,wfxiang08/gh-ost,wfxiang08/gh-ost