Add docs for registry proxy addon

update releases.json to include v1.2.0

Fix the reportcard: gofmt, golint and gocyclo

Update start.jpg to v1.2

Add release notes for v1.2.0

Add golint and gocyclo smaller make targets

Remove extraneous whitespace from GitHub issue templates

Bump Makefile version to v1.2.0 to prepare for a release

Allow --kubernetes-version to be specified without the leading v

Provide warning message for unnecessary sudo

Universally redirect stdlog messages to glog

Make markdownlint happy about whitespace

Adjustment titles of Chinese & English issue template titles

Enable running containers with Podman

Use non-list YAML format for issue labels, simplify text

zh-CN: Use non-unicode percent signs for proper interpolation

Use "make mdlint" to check current status

Here is the report (from gocyclo), before:

21 tests (*SSHServer).Start pkg/minikube/tests/ssh_mock.go:76:1
19 cmd runStart cmd/minikube/cmd/start.go:173:1
18 integration testTunnel test/integration/tunnel_test.go:40:1
17 extract checkCallExpression pkg/minikube/extract/extract.go:198:1
17 kubeadm TestGenerateConfig pkg/minikube/bootstrapper/kubeadm/kubeadm_test.go:133:1
16 kvm (*Driver).deleteNetwork pkg/drivers/kvm/network.go:153:1

The standard "fmt" target will also rewrite

Add return code, by checking for empty output

Also fix the broken fmt and reportcard ones:

Recursive variable 'SOURCE_DIRS' references itself (eventually).