Merge branch 'stable-3.0' into stable-3.1

* stable-3.0:
  Replace unused postgresql jar with manual site copy
  Align postgresql version used with gerrit core one
  Stop shipping core dependencies within plugin jar
  Sort CONDUCTOR_DEPS and EXECUTOR_DEPS alphabetically
  Adapt documentation version link in README for e2e
  Add README introducing e2e plugin test scenarios

Change-Id: Ib88ac91a4dded59d7fefd971900c1bd6465ba146