jicofo,jigase: add ability to extend the config file

jicofo/rootfs/etc/cont-init.d/10-config

@@ -18,6 +18,9 @@ if [[ "$JICOFO_AUTH_PASSWORD" == "$OLD_JICOFO_AUTH_PASSWORD" ]]; then
 fi
 
 tpl /defaults/sip-communicator.properties > /config/sip-communicator.properties
+if [[ -f /config/custom-sip-communicator.properties ]]; then
+    cat /config/custom-sip-communicator.properties >> /config/sip-communicator.properties
+fi
 
 if [[ ! -f /config/logging.properties ]]; then
     cp /defaults/logging.properties /config

jigasi/rootfs/etc/cont-init.d/10-config

@@ -12,6 +12,9 @@ if [[ "$JIGASI_XMPP_PASSWORD" == "$OLD_JIGASI_XMPP_PASSWORD" ]]; then
 fi
 
 tpl /defaults/sip-communicator.properties > /config/sip-communicator.properties
+if [[ -f /config/custom-sip-communicator.properties ]]; then
+    cat /config/custom-sip-communicator.properties >> /config/sip-communicator.properties
+fi
 
 if [[ ! -f /config/logging.properties ]]; then
     cp /defaults/logging.properties /config