Add configurable path to database and docker-compose sample

docker-compose.yml-sample

@@ -0,0 +1,12 @@
+---
+version: "2.1"
+services:
+  linkwallet:
+    image: tardisx/linkwallet:latest
+    container_name: linkwallet
+    command: /app/linkwallet -db-path=/data/linkwallet.db
+    volumes:
+      - /home/username/.linkwallet:/data
+    ports:
+      - 8109:8080
+    restart: unless-stopped