Implement a more dynamic celery queue system

* Meant to be a starting point to more efficiently manage work routing
  and to balance work across all tower nodes
* Integrate flower as a dev tool that starts alongside other nodes.
  Helpful for observing and monitoring the queues/exchanges
* For the moment, force the task manager to only run on one node (not
  sure if this is needed)
* Define queues and routes for all task work
* Bump celery version to 3.1.23
* Expose flower through haproxy

tools/docker-compose/haproxy.cfg

@@ -17,6 +17,11 @@ frontend localnodes
     mode http
     default_backend nodes
 
+frontend flower
+    bind *:5555
+    mode http
+    default_backend flower_nodes
+
 backend nodes
     mode http
     balance roundrobin
@@ -29,6 +34,18 @@ backend nodes
     server tower_2 tower_2:8013 check
     server tower_3 tower_3:8013 check
 
+backend flower_nodes
+    mode http
+    balance roundrobin
+    option forwardfor
+    option http-pretend-keepalive
+    http-request set-header X-Forwarded-Port %[dst_port]
+    http-request add-header X-Forwarded-Proto https if { ssl_fc }
+    #option httpchk HEAD / HTTP/1.1\r\nHost:localhost
+    server tower_1 tower_1:5555
+    server tower_2 tower_2:5555
+    server tower_3 tower_3:5555
+
 listen stats
     bind *:1936
     stats enable