Mixing public and protected news in a single news list

This extension is considered revision of intention basically shared with extension tx_teasing_feed.

In opposition to default news list module this extension's news list module (given as an addon) isn't dropping currently protected news archives but using different template for rendering those archives' news items mixing them all in a single news list. This way it's possible to promote protected news items with reduced content in public e.g. for improving search engine optimization on a news portal providing beneficial news to a closed group of subscribers. Different from previous implementation in tx_teasing_feed, this method always works dependently on current visitor's authorization, thus promoting news associated with different member groups to members of other member groups e.g. to promote extending subscription.