Check hidden status of translation pages

As part of our XAR plugin checks, we currently check that a base translation page named *Translations.xml should have a hidden property set to true.
First of all it looks like a bad practice to detect same based only on the name pattern, instead of detecting them based on the presence of a TranslationDocumentClass object, since we might miss some translations not following this page name pattern.

Now we're also missing to check that the hidden property value of the translated pages always follow the rule of their default page translation. If the default page translation contains a TranslationDocumentClass the hidden property should always be true, but in case of standard wiki page (like Sandbox.WebHome) it all depends on the value given by the default language page.