Updates to ParentArticles don't show up on dynamic pages when using the development server

[NickSto]

ParentArticles were introduced in #1692 to allow both Articles and VueArticles to be listed in dynamic pages. It succeeds in this (mostly), but it looks like changes won't show up on those pages when using the development server.

This makes some sense when modifying existing pages, since the way ParentArticles are created (in nodeModifier.processArticleType()) has no facility for updating an existing page. Stranger is the fact that entirely new ParentArticles don't appear.