* Reverting the last commit, if you just want to use a message from the user

* Reverting the last commit, if you just want to use a message from the user
  language if it exists use wfMsg() instead of wfMsgForContent(), don't
  rewrite the entire message selection code when we have libraries to handle
  that, furthermore, this *should* use the content language by default, since
  it's only in rare cases, such as the commons, when you want the opposite,
  this should be overriden via a configuration ($wgForceUIMsgAsContentMsg)
  there instead of changing the main code.