added MARIADB_HOST variable

if one needs an external database

docker-compose.yml

@@ -7,7 +7,7 @@ services:
       - mariadb
     environment:
       - TZ=${PI_TIMEZONE}
-      - IPAM_DATABASE_HOST=mariadb
+      - IPAM_DATABASE_HOST=${MARIADB_HOST}
       - IPAM_DATABASE_NAME=${MARIADB_DATABASE}
       - IPAM_DATABASE_USER=${MARIADB_USER}
       - IPAM_DATABASE_PASS=${MARIADB_PASSWORD}