- adds required `GCLOUD_SDK_VERSION` `--build-arg` to `Dockerfile`
- removes `Dockerfile.1.10`, `Dockerfile.1.11` (can now be customized via `GCLOUD_SDK_VERSION` build arg)
- removes `bin/dist`; replaced with `make`-based implementation
- adds several misc config / rc files
- updates `README`, `DOCS.md` to reflect changes, address linting

refactor build tooling

- adds required `GCLOUD_SDK_VERSION` `--build-arg` to `Dockerfile`
- removes `Dockerfile.1.10`, `Dockerfile.1.11` (can now be customized via `GCLOUD_SDK_VERSION` build arg)
- removes `bin/dist`; replaced with `make`-based implementation
- adds several misc config / rc files
- updates `README`, `DOCS.md` to reflect changes, address linting

Apply suggestions from code review

Co-Authored-By: Chris Montoro <[email protected]>

- remove cloud-sdk stage from Dockerfile
- remove bin/install-kubectl ; add installation steps inline within Dockerfile
- replaced references to CLOUD_SDK_VERSION / GCLOUD_SDK_VERSION with GCLOUD_SDK_TAG
- move developer focused documentation to CONTRIBUTING.md
- move .PHONY blocks to the line above each related target definition
- add coverage.out make target
- add check for go v 1.12+
- rename docker-release, docker-run-local make targets
- add terraform integration to automate test resource provisioning
- update DOCS.md to support deep links to individual parameters within API reference
- update local-example app, image, API_TOKEN variable names to avoid potential confusion with drone-gke parameters