Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Set Gerrit to 2.14.20
  Set Gerrit to 2.15.13
  Set version to 2.13.14 and require Java 8
  Set version to 2.13.13
  Set Gerrit to 2.15.12
  Set Gerrit to 2.14.19
  Set Gerrit to 2.15.11

Change-Id: I1f9d20e4b2ca2a785b3bf7b97241051a4d206e5b