Merge POC into consul-k8s

[thisisnotashwin]

Introduce changes made in the POC to crd base branch.

How I've tested this PR:
Run the controller in my GCR cluster and create ServiceDefaults.
Steps:

1. kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/download/v0.15.2/cert-manager-legacy.yaml
2. helm install consul hashicorp/consul --set server.bootstrapExpect=1 --set server.replicas=1
3. make ctrl-deploy IMG=ashwinvenkatesh/consul-k8s:latest
4. kubectl apply -f defaults.yaml

deafults.yaml

apiVersion: consul.hashicorp.com/v1alpha1
kind: ServiceDefaults
metadata:
  name: servicedefaults-sample
spec:
  protocol: "http"

Check controller logs to see reconcile successful.

How I expect reviewers to test this PR:
Repeat above steps. Try and break stuff.

Checklist:

• Tests added
• CHANGELOG entry added (HashiCorp engineers only, community PRs should not add a changelog entry)

[lkysow]

🎉 wow this was a lot of code! We can pair on some of these suggestions.

[kschoche]

Looks awesome! A lot of stuff going on here, and only a few non-blocking comments which can be discussed when we try to merge to master!

Great work!