Update to version 5.19

1. Highlights

• Direct import of real estate from Immowelt via the Immowelt API
• New galleria.io Slideshow Themes 'Azur' and 'Folio' selectable in the Customizer

2. improvements

• ImmoScout24: Support for the countries DEU/AUT/ESP/FRA/ITA/BHS/HRV
• ImmoScout24: Support for 'Certificate of eligibility for housing required'
• Watch list: The system regularly checks whether all properties on the watch list still exist
• 22 further improvements
• 5 new filters