* show UTC in in verbose messages of function calls that is the format of date string in the JSON file * date_iso_to_seconds: correct date_string * get_mediapool_retensiondays(): new function * add_retensiondays(): new function * get_retensiondays(): new function * update_mediapool_retensiondays(): new function Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>