Repalce & with & in HTML documents.

This is not a long term solution, but it's a quick fix to solve URL problems when converting to a static site via httrack.

src/main/java/org/qortal/api/HTMLParser.java

@@ -78,11 +78,17 @@ public class HTMLParser {
                     }
                 }
             }
-            return document.html().getBytes();
+            String html = document.html();
+            html = this.replaceAmpersands(html);
+            return html.getBytes();
         }
         return data;
     }
 
+    private String replaceAmpersands(String html) {
+        return html.replace("&", "&");
+    }
+
     private boolean shouldReplaceLink(String elementHtml) {
         List<String> prefixes = new ArrayList<>();
         prefixes.add("http"); // Don't modify absolute links