* added SIGTERM handler for graceful docker shutdown
* added error message
* added example for bitcoind running on the host undockered
* added docker-compose and extended example
* added docker-compose section to README
* addes some note for rpcallowip
* added restart policy
* added DB folder for persistent data
* added $NETWORK as prefix for database path to not get in conflict with testnet setup
* used env variables for stratum and api ports
