Add script to deploy into a single node minikube instance

[ansiwen]

This script takes an existing minikube instance in which it creates a
block device image under mnt/vda1/heketi-bricks.img that is connected
to /dev/loop1. Then gk-deploy is started in the single-node mode on
top of minikube and a default storage class gluster-storage is
created.

This change is 

[centos-ci]

Can one of the admins verify this patch?

[jarrpa]

I like the idea! Though please add an option to control the size of the bricks file.

I also don't know much about minikube, what is the ISO you're downloading?

[ansiwen]

@jarrpa: I'm nor sure it makes sense to make the size of the bricks file configurable. It is a sparse file of 10GB and sits inside an image of an hard-coded size of 13GB, that is created by minikube. I can't think of a scenario where it is useful to make it smaller or bigger. Do you have one?

Creating the ISO was actually the biggest effort for this PR. 😅 I added some background on it in the commit notes and how to create it by yourself.

[jarrpa]

....ah, okay! In that case could you just provide hints on how to create the minikube image as comments in the script? I can almost guarantee that people won't think to look in the commit notes.

[ansiwen]

@jarrpa I pushed a new version which only deploys on an existing minikube deployment, since the latest version of minikube includes the heketi/gluster dependencies now in the latest release, after this had been merged: kubernetes/minikube#2925

[jarrpa]

LGTM!