Install CRDs by using the new crd-install hook

[migmartri]

NOTE: This is an alternative approach to #820

Helm 2.10 allows installing CRDs in a controlled way which seems to fix our issue #819

I have managed to successfully complete this scenario #813 in GKE by using an upgraded version of Helm.

A side effect of using this hook is that now we do not need the bootstrap job and we can add the repositories in pre or post install.

$ helm version
Client: &version.Version{SemVer:"v2.11.0", GitCommit:"2e55dbe1fdb5fdb96b75ff144a339489417b146b", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.11.0", GitCommit:"2e55dbe1fdb5fdb96b75ff144a339489417b146b", GitTreeState:"clean"}

The patch also adds the requirement in the Chart.yaml file so it is clear that there is a min requirement to make it work.

NOTE: "helm.sh/hook": crd-install is only applied on installation so if you delete the crd and then update it will not get created. It does not update it either.

Fixes #819

[prydonius]

lgtm, check to see if we can remove the bootstrap job. We should also add documentation about the minimum version of Helm we support in the README, getting started and Helm chart README (feel free to do that in a separate PR).