Add README note

README.md

@@ -2,6 +2,11 @@
 
 ## Build Setup
 
+Create the database container image:
+
+    cd fda-container-managing-service/rest-service/src/main/resources
+    docker build --tag rdr-postgres:1.0 .
+
 ```bash
 # First generate jars for discovery,database,container and query services
 $ mvn clean package