LDEV-2079 use the same language as users in pixlradded an admin page with a tet field that has all the currently supported languages in a comma-seperated string which can be updated by system admins if there are new languages added to pixlr that we are unaware of
fixing pixlr tool so blank image is always tested against default content, in case the default content is changed by the user and is no longer the blank.jpg file