Fixing issue with not being able to access custom fields in pages:children.

Now the plugin checks to see what page types/streams are needed and grabs just the entries needed. It only does it if it finds {{ custom_fields }} in the content of the tag.

Since the children of a page can have several different page types (and several different streams), this seems like the most economical way to do things. Each new page type you have requires a query.

You can also check the page type with the {{ page_type_slug }} and {{ page_type_title }} variables.