Content Pages and Technical pages configuration of the xar plugin should be file paths instead of file names

The xar plugin takes configuration for content pages and technical pages, handling default language and hidden status differently for the 2 types of pages.

However, this configuration only takes page names and not page paths.
The path is almost mandatory, since WebHome.xml is such a common name that it may be both content and technical page, so we should be able to have more control for this configuration.