Add bot user agent detection (close #32)

lib/gatheranalytics.php

@@ -21,6 +21,13 @@ if (!$database->has("settings", ["AND" => ["siteid" => getsiteid(), "key" => "an
             throw new Exception("Do-Not-Track header detected, skipping analytics");
         }
 
+        $bots = json_decode(file_get_contents(__DIR__ . "/bots.json"), true);
+        foreach ($bots as $bot) {
+            if (preg_match('/' . $bot['pattern'] . '/', $_SERVER['HTTP_USER_AGENT'])) {
+                throw new Exception("Bot/crawler detected, skipping analytics");
+            }
+        }
+
         $time = date("Y-m-d H:i:s");
 
         /**