Assign frame ranges to servers based on their CPU count (#19)

* Expose renderer availability in status api

* Remove redundant is_available_for_job API call

* New server split logic by cpu and moved to server_helper.py

* Remove old dead code

* Add RenderStatus.WAITING to proxy categories

lib/workers/base_worker.py

@@ -274,6 +274,7 @@ class BaseRenderWorker(Base):
         logger.debug("Starting post-processing work")
         self.post_processing()
         self.status = RenderStatus.COMPLETED
+        logger.info(f"Render {self.id}-{self.name} completed successfully after {self.time_elapsed()}")
 
     def post_processing(self):
         pass