Merge branch '23563-document-presenters' into 'master'

app/controllers/projects/builds_controller.rb

app/models/ci/build.rb

app/models/concerns/presentable.rb

app/policies/base_policy.rb

app/presenters/README.md

app/presenters/ci/build_presenter.rb

app/views/projects/builds/show.html.haml

lib/gitlab/view/presenter/base.rb

lib/gitlab/view/presenter/delegated.rb

lib/gitlab/view/presenter/factory.rb

lib/gitlab/view/presenter/simple.rb

spec/lib/gitlab/view/presenter/base_spec.rb

spec/lib/gitlab/view/presenter/delegated_spec.rb

spec/lib/gitlab/view/presenter/factory_spec.rb

spec/lib/gitlab/view/presenter/simple_spec.rb

spec/models/concerns/presentable_spec.rb

spec/policies/base_policy_spec.rb

spec/presenters/ci/build_presenter_spec.rb