[kn-admin]As a Knative administrator, I want to list autoscaling configs which apply to overall Knative platform.

[zhanggbj]

A developer may set some autoscaling configs like --limits-cpu or --limits-memory as what kn service create described today. However, a Knative administrator may need to update some overall configs like stable-window or panic-window-percentage or ticker-interval for the whole Knative platform. The kn-admin will list all the config we support to update by kn-admin

$ kn admin autoscaling list

• Stable-window
• panic-window-percentage
• ticker-interval

If there're any other autoscale configs which should be controlled by Knative administrator, please feel free to leave a comment in this issue. Thanks!

[zhanggbj]

Pending on #71 to decide all the config we need.

[zhanggbj]

/assign