Merge branch 'stable-2.8'

* stable-2.8:
  Update 2.8.2 release notes
  Make the message of 'Cherry Picked' informative
  Show error message when the commentlink is configured wrongly

Conflicts:
	gerrit-server/src/main/java/com/google/gerrit/server/change/CherryPickChange.java

Change-Id: I82a7ac51f31fec83166ecad26e65d66623d2cda4