Moved show warning method to timelines controller.

I don't actually think this was exactly related to the error in bug 7186 - i think that was because there was somehow old code - but this was also preventing the warning message from being displayed.
Moved showWarning method back to container directive.
Merge pull request #1225 from opf/fix/timelines-show-warning-7186

Moved show warning method to timelines controller.