Kubernetes Backend; Go Module Support

[adamstruck]

For setup see: https://github.com/ohsu-comp-bio/funnel/blob/kube/deployments/kubernetes/README.md

closes #414

TODO:

• More documentation
• Map disk request to volume in job template

[kellrott]

Tested against K8S cluster built using https://github.com/ohsu-comp-bio/openstack_k8s
When submitting a job, Funnel set it to a 'Queued' state and never updated. Looking into the logs found:

{"error":"creating job: jobs.batch is forbidden: User \"system:serviceaccount:default:default\" cannot create resource \"jobs\" in API group \"batch\" in the namespace \"default\"","level":"error","msg":"error submitting task to compute backend","ns":"server","taskID":"bpq39a19jgp5u6qfrh70","time":"2020-03-20T03:12:40Z"}

This setting probably needs to be added to the documentation.

[adamstruck]

@kellrott I think this PR is ready for merge

[kellrott]

It's been tested on multiple K8S setups, so looks good.