resourceloader: Set a Title on context-created messages

resourceloader: Set a Title on context-created messages

Ensure that messages created using ResourceLoaderContext::msg() have a
title set so they don't trigger the GlobalTitleFail log. We use a dummy
title since there is no real title we can use here, and the cache
doesn't vary on a title anyways. This particular title was picked
especially for Roan.

This patch should quiet the GlobalTitleFail logs for
MFResourceLoaderParsedMessageModule and VisualEditorDataModule.

Change-Id: I502faa22776e1cb34a6ef17be96567f121c80081