Encode URL properly (lobid-gnd#408)

Question marks weren't encoded. It's better to use a library.

gatsby/lobid/static/imagesproxy.php

@@ -1,10 +1,13 @@
 <?php
-        $url = $_GET['url'];
-        $url=str_replace(" ", "%20", $url);
+        $url = implode("/", array_map("rawurlencode", explode("/", $_GET['url'])));
+        // restore the colon of the protocol
+        $positionOfColon = strpos($url,"%");
+        $url= substr_replace($url,":",$positionOfColon,3);
         $ch = curl_init();
         curl_setopt($ch, CURLOPT_URL, $url);
         curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
         curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: text/xml","User-Agent: imagesproxy/0.2 (https://lobid.org/)"));
+
         curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
         $filename = basename($url);
 
@@ -27,6 +30,6 @@
 
         header('Content-type: ' . $ctype);
         echo $output = curl_exec($ch);
-        curl_close($ch); 
+        curl_close($ch);
 ?>