bbbmiddleware: add hsmserialport to config (#288)

Because:
* The HSM serial port (default: /dev/ttyS2) needs to be passed by
  command line to the bbbmiddleware.
* This is what the /etc/bbbmiddleware/bbbmiddleware.conf is for, so
  the configuration is stored in Redis and loaded as environment
  variable into systemd unit.

This commit:
* adds Redis keys bbbmiddleware:datadir and bbbmiddleware:hsmserialport
* adds these to the config template bbbmiddleware.conf.template
* loads them as env variables and passes them to the binary as cli
  arguments in the systemd unit

armbian/base/config/redis/factorysettings.txt

@@ -15,6 +15,8 @@ SET base:updating 0
 SET base:setup 0
 
 SET middleware:passwordSetup 0
+SET middleware:datadir /data/bbbmiddleware
+SET middleware:hsmserialport /dev/ttyS2
 
 SET tor:base:enabled 1
 SET tor:ssh:enabled 0

armbian/base/config/templates/bbbmiddleware.conf.template

@@ -1 +1,3 @@
 {{ #output: /etc/bbbmiddleware/bbbmiddleware.conf }}
+DATADIR={{ middleware:datadir #default: /data/bbbmiddleware }}
+HSMSERIALPORT={{ middleware:hsmserialport #default: /dev/ttyS2 }}

armbian/base/rootfs/etc/systemd/system/bbbmiddleware.service

@@ -10,7 +10,8 @@ After=multi-user.target bitcoind.service
 EnvironmentFile=/etc/bbbmiddleware/bbbmiddleware.conf
 ExecStartPre=/opt/shift/scripts/systemd-bbbmiddleware-startpre.sh
 ExecStart=/usr/local/sbin/bbbmiddleware \
-    -datadir=/data/bbbmiddleware
+    -datadir=${DATADIR} \
+    -hsmserialport=${HSMSERIALPORT}
 
 # Process management
 ####################