Add a script to generate the screenshots for all the available languages.

Change the format of data.js generated file.
Add Fragment to the URL to limit the number of displayed languages.
Add a checkbox to display all screenshots or not.

screenshots/html/screenshots.css

@@ -50,10 +50,19 @@ img {
   display: block;
 }
 
+.missing {
+    text-align: center;
+}
+
 th {
     background: #0DBD8B;
 }
 
+br {
+   display: block;
+   margin: 4px 0;
+}
+
 #form_container {
     margin: 0px auto;
 }