some changes for docker setup (#9)

* 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

.env.example

@@ -1,4 +1,10 @@
+# bitcoin node running in your private network 192.168.1.0/24
 BITCOIN_RPC_URL=http://192.168.1.100
+
+# bitcoin node running undockered on the same PC
+# needs to add rpcallowip=172.16.0.0/12 to your bitcoin.conf
+#BITCOIN_RPC_URL=http://host.docker.internal
+
 BITCOIN_RPC_USER=
 BITCOIN_RPC_PASSWORD=
 BITCOIN_RPC_PORT=8332
@@ -31,4 +37,4 @@ ENABLE_PROXY=true
 
 BRAIINS_ACCESS_TOKEN=
 
-PROXY_PORT=3333
+PROXY_PORT=3333