Remove comment in request manager
Server accepts additionnal info from worker: systemSwapPercentage

This data is stored in the rendernode model and can be queried with pul_rn
Older version of the worker (<1.6.13) will still work
Update worker info

- Worker has an additionnal value indicating the percentage of swap used.
- A delay can be defined to force a full update of the worker after
  a long period of time. This ensures that even without registering worker,
  the data will be fresh (delay is set to 5mn by defaut).
  This delay should be much higher thant worker heartbeat (8s), usually several minutes
- update display in pul_rn
Merge branch 'feature/protect_worker_swap' into develop