MUA: Echte Unraid-Plugin-Struktur

- plugin/mua.plg: <!DOCTYPE PLUGIN> XML mit <FILE Run> + <INLINE>
- plugin/plugin.json: Metadaten
- scripts/rc.mua: SysVinit-Service (statt systemd)
- scripts/plugin.php: WebGUI-Tab (Settings > MUA)
- README.md: Aktualisiert
- Alte Dateien entfernt (MUA.plg, mua.service, install/update/remove.sh)

plugin/plugin.json

@@ -0,0 +1,9 @@
+{
+    "name": "mua",
+    "author": "Michael",
+    "version": "1.0.0",
+    "minver": "7.0.0",
+    "pluginDirectory": "/usr/local/emhttp/plugins/mua",
+    "configDirectory": "/boot/config/plugins/mua",
+    "port": 3002
+}