rtorrent: set more env, externalize to env file

rtorrent.env

@@ -0,0 +1,3 @@
+VPN_ENABLED=no
+WEBUI_USER=lukas
+WEBUI_PASS=kralovna

rtorrent.yml

@@ -3,12 +3,15 @@ services:
   rtorrent:
     image: binhex/arch-rtorrentvpn
     container_name: rtorrent
-    environment:
-      - VPN_ENABLED=no
     volumes:
       - "${DOCKER_STORAGE_PATH}/rtorrent/config:/config"
       - ${STORAGE_PATH}/seed:/data
       - /etc/localtime:/etc/localtime:ro
+    environment:
+      - PUID=${PUID}
+      - PGID=${PGID}
+    env_file:
+      - rtorrent.env
     ports:
       - "9080:9080"
       - "9443:9443"