Improve manual actions code and add model, service and feature tests

app/controllers/projects/builds_controller.rb

app/models/ci/build.rb

app/models/deployment.rb

app/views/projects/ci/builds/_build.html.haml

app/views/projects/ci/pipelines/_pipeline.html.haml

app/views/projects/deployments/_actions.haml

app/views/projects/deployments/_deployment.html.haml

app/views/projects/deployments/_playable.html.haml

app/views/projects/environments/_environment.html.haml

app/views/projects/environments/index.html.haml

config/initializers/relative_naming_ci_namespace.rb

doc/ci/yaml/README.md

spec/factories/ci/builds.rb

spec/features/environments_spec.rb

spec/features/pipelines_spec.rb

spec/models/build_spec.rb

spec/models/ci/pipeline_spec.rb

spec/models/deployment_spec.rb

spec/services/ci/create_pipeline_service_spec.rb