The current style of calling event.addresponse hinders translation and response middleware from being authored

The current style of calling event.addresponse will not work well for adding translation of responses (or other response middleware that may require altering template strings or variables before merging).

At present modules call addresponse as follows:
  event.addresponse(u"%s source loaded" % source)

To allow for response middleware like translation services, addresponse should be modified to allow it to be called:
  event.addresponse(u"%s source loaded",source)

Adding translation will mean we can build language packs for ibid, so we could have friendly or formal english language packs.