Add details for network, dashboard and K8S version choices

[scaleoutsean]

Is this a bug report or feature request?

• Bug Report

Bug Report

Expected behavior:

• K8S_DASHBOARD=true: I'd expect I should be able to run kubectl proxy and use it, but I couldn't make that work. Now I just (re) install it myself (and it works) after it's supposedly been installed. If this choice results in K8S dash being installed, where is it and how to use it?
• KUBERNETES_VERSION - it's not clear how this should be set and what happens if it's not. It says: "KUBEADM_INIT_FLAGS will be set to --kubernetes-version=$KUBERNETES_VERSION if unset" sounds as if not providing this results in --kubernetes-version='' (I know it doesn't). It is also not clear whether this should be v1.23 or 1.23. K8S_DASHBOARD_VERSION has a version string example, but this variable does not. I know I can dig through scripts or log to figure it out, but if this was documented it'd be better.
• CLUSTER_NAME - it seems default upstream behavior is that cluster name is also set in Dashboard (Settings > Global Settings > Cluster name) but in this case that setting is left empty when cluster name isn't set.
  
• NODE_IP_NW - maybe some detail on network types and impact of those choices would be helpful

Deviation from expected behavior:

• K8S_DASHBOARD=true - it's hard to see the effects of this setting
• KUBERNETES_VERSION=1.15 - causes install to fail. Educated guess would be v1.15, but it'd be better have it spelled out.
• CLUSTER_NAME= - if dashboard is installed, dashboard should pick cluster name
• NODE_IP_NW - I wasn't sure what the installer would do, but I thought it might create a bridged network if I set this range to my LAN range, or that it'd use intnet type (rather than vboxnet), or maybe ask me to pick one.

Environment:

• Bionic 18.04
• kernel 4.15.0-54
• make versions output:

=== BEGIN Version Info ===
Repo state: 62d403b37d433db7d3eed6d8a98136837441aadb (dirty? NO)
make: /usr/bin/make
kubectl: /usr/bin/kubectl
grep: /bin/grep
cut: /usr/bin/cut
rsync: /usr/bin/rsync
openssl: /usr/bin/openssl
/dev/urandom: OK
Vagrant version:
Vagrant 2.2.5
vboxmanage version:
6.0.10r132072
=== END Version Info ===

[galexrt]

• K8S_DASHBOARD should be fixed now.
• KUBERNETES_VERSION Added clarification to README in upcoming commit.
• CLUSTER_NAME is the part of the name of the VMs and other directories, not the Kubernetes cluster due to kubeadm init limitations.
• NODE_IP_NW is used as the first three segments of the IPv4 addresses for the VMs and meant for node to node communication. Let's continue in Network selection #48.