Remove Gerrit v2.13, plugins and Buck builds

Gerrit v2.13 is now officially unsupported and it is time
to remove the historical plugin builds and support for Buck
builds altogether.

Change-Id: I08825d111195ae7ab4d24f8fd4b7dff82bd1e0e7
71 files changed
tree: 772ef364c167080c5342e13d33af6a3be1e2590b
  1. jenkins/
  2. jenkins-docker/
  3. worker/
  4. .gitignore