Refactor: DistributedJobManager with pub/sub status change notifications (#25)

* Add pubsub to render_queue and base_worker

* Refactor: Convert ZeroconfServer to Singleton with Class Methods

* New API for subjob servers to notify parent job servers of status changes

* Refactor: Move all subjob related methods to distributed_job_manager.py

* Rewrite for wait_for_subjobs

* Fix: DistributedJobManager.find_available_servers() takes 1 positional argument but 3 were given

* DistributedJobManager should now notify / be notified abotu background job changes

* Fix the make_ready api. Change children keyname to be id@hostname so it can be unique

* Fixes

* Image sequence to movie needs to find the actual start frame

* Fix: subjob_status_change did not return a valid response

* Fix client renderer selection

* Small fix for subjob status checking

* Fix issue with divide_frames_equally

* Fix issue where downloads were not occurring

* Fix issue where old status was being reported

* Add docstrings and code cleanup

lib/client/dashboard_window.py

@@ -44,8 +44,8 @@ class DashboardWindow:
         self.added_hostnames = []
 
         # Setup zeroconf
-        self.zeroconf = ZeroconfServer("_zordon._tcp.local.", socket.gethostname(), 8080)
-        self.zeroconf.start(listen_only=True)
+        ZeroconfServer.configure("_zordon._tcp.local.", socket.gethostname(), 8080)
+        ZeroconfServer.start(listen_only=True)
 
         # Setup photo preview
         photo_pad = tk.Frame(self.root, background="gray")
@@ -299,7 +299,7 @@ class DashboardWindow:
                         tree.item(item, values=new_values)
                     break
 
-        current_servers = list(set(self.zeroconf.found_clients() + self.added_hostnames))
+        current_servers = list(set(ZeroconfServer.found_clients() + self.added_hostnames))
         for hostname in current_servers:
             if not self.server_proxies.get(hostname, None):
                 new_proxy = RenderServerProxy(hostname=hostname)