Introudce init command

src/server/install/index.md

@@ -36,12 +36,13 @@ $ docker-compose -f docker-compose.yml up
 ```
 ​​
 ### Initialise database
-If server is started for the first time, database needs to be initialised and super-user created (set admin username, password and email):
+If server is started for the first time, database needs to be initialised and super-user created. Use the `init` command which will perform it automatically (check the command outputs to get the password):
 ```shell
-$ docker exec merginmaps-server flask init-db
-$ docker exec merginmaps-server flask user create <username> <password> --is-admin --email <email>
+$ docker exec merginmaps-server flask init
 ```
 
+If you don't have `CONTACT_EMAIL` variabe set, you will be asked to provide a super user email using the `-e`/`--email` option. The `init` will also check your server setup (celery jobs, emails, etc.) and print out a list of missing variables. If you see any errors in the console output, you can run the command again as the database and super user will not be re-initialized.
+
 ### Setup environment
 ​
 Now tweak deployment settings by modifying environment variables. You have to fix all variables marked as required in this list of [environment variables](../administer/environment.md). Some of the most common issues with custom deployments are listed in the [troubleshoot](../troubleshoot/index.md) section.