Add docker install readme

docs/DOCKER_INSTALL.md

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+# Bolt card service installation using Docker
+
+### install Docker engine and Docker compose
+
+[Docker engine download & install](https://docs.docker.com/engine/install/)
+[Docker compose download & install](https://docs.docker.com/compose/install/)
+
+### Set up the boltcard server
+edit `.env` to set up the database connection
+edit `settings.sql` to set up [bolt card system settings](SETTINGS.md)
+edit `Caddyfile` to set the boltcard domain name
+
+### https setup
+
+set up the domain A record to point to the server
+
+set up the server hosting firewall to allow open access to https (port 443) only
+
+
+### service bring-up and running
+```
+$ docker volumes create caddy_data
+// add -d for detached mode
+$ docker-compose up -d
+```
+
+### stop docker
+```
+$ docker-compose down
+```
+To delete the database and reset the docker volume, run `docker-compose down --volumes`
+*NOTE:  caddy_data volume won't be removed even if you run `docker-compose down --volumes` because it's an external volume.*  
+
+
+#### running create bolt card command
+-  `docker exec boltcard_main createboltcard/createboltcard`  to see options
+-  `docker exec boltcard_main createboltcard/createboltcard -enable -allow_neg_bal -tx_max=1000 -day_max=10000 -name=card_1`  for example
+-  this will give you a one-time link in text and QR code form