Reworks plugin loading and structure

Implements #4358

scripts/plugins/alerts/security/syn_scan_alert/manifest.lua

@@ -0,0 +1,10 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+return {
+  title = "SYN Scan detector",
+  description = "Detects SYN scan attacks on hosts and networks and triggers alerts",
+  author = "ntop",
+  dependencies = {},
+}