GeoIP lookup

Server-side proxy for ipapi.co's IP geolocation lookup, used by the Timezone/GeoLocation "Lookup"/"Detect" buttons on settings.php. ipapi.co does not send Access-Control-Allow-Origin, so the browser can't call it directly from FPP's UI (blocked by the Same Origin Policy) - PHP isn't subject to that, so we fetch it here and hand back the same JSON.