Docker fix: add ensubst

docker/dm/conf/bitcoin.conf

@@ -0,0 +1,30 @@
+[main]
+## Bitcoin testnet
+## default: false
+testnet=$DM_TESTNET
+
+[endpoint]
+## default: tcp://mainnet.libbitcoin.net:9091
+#url=tcp://testnet.libbitcoin.net:19091
+
+[transaction]
+## Transaction minimum output value
+## default: 200
+#min_output=200
+
+[miner]
+## Transaction fee as a percentage of the deal amount
+## ATTENTION: If the value is specified as a percentage, you MUST indicate the sign “%”,
+##            otherwise it will be a FIXED value in satoshi.
+
+## Transaction fee for miner
+## default: 1%
+#fee=1%
+
+## Transaction fee for miner (minimal)
+## default: 200
+#min=200
+
+## Transaction fee for miner (maximum)
+## default: 2000
+#max=2000