Merge branch 'stable-3.1'

* stable-3.1:
  Add some commands the build documentation
  Remove standalone build mode
  Add an executable README that sets gc-executor up
  Upgrade bazlets to latest stable-3.1 to build with 3.1.11 API

Change-Id: Ie4575e2885b74307a23e1dcf668814e13c80b7de