Add zh_CN translatioin for five plugins

Again, these are incomplete, but are almost enough for daily work.

The five plugins are:
* openXBannerTypes
* openXDeliveryLimitations
* openXInvocationTags
* openXMaxMindGeoIP
* openXReports
Merge pull request #139 from leesah/plugins-gettext

Add zh_CN translatioin for five plugins