Move Plex to API-driven plugin and fix NoClassDefFoundError on startup

server/src/main/java/dev/plex/services/impl/UpdateCheckerService.java

@@ -0,0 +1,33 @@
+package dev.plex.services.impl;
+
+import dev.plex.services.AbstractService;
+import org.bukkit.Bukkit;
+
+public class UpdateCheckerService extends AbstractService
+{
+    private boolean newVersion = false;
+
+    public UpdateCheckerService()
+    {
+        super(true, true);
+    }
+
+    @Override
+    public void run()
+    {
+        if (!newVersion)
+        {
+            if (plugin.getUpdateChecker().getUpdateStatusMessage(Bukkit.getConsoleSender(), false, 1))
+            {
+                newVersion = true;
+            }
+        }
+    }
+
+    @Override
+    public int repeatInSeconds()
+    {
+        // Every 30 minutes
+        return 1800;
+    }
+}