Issue 2948: fix "kubectl get events" result not sorted

Fixes #2948
* Added a "TIME" column to results from both "kubectl get events" and "kubectl describe pod x"
* Added code to sort the result from "kubectl get events" by event timestamp
  * Verified that sorting has negligible impact on runtime while sorting 8000 events
* Confirmed that "kubectl describe pod x" is already sorting results by time
* Added unit tests to verify both "kubectl get events" and "kubectl describe pod x" results are sorted by time.

This test is sort of a change detector-- every change to describe pod's output is going to (potentially) change the number of lines and where events are printed. I'd recommend changing this to grep every line so that it doesn't matter what lines they come out, as long as they come out in order, or searching for the line with the event headers and then looking for the events in the lines after that.