Updated tablegen.py to process the configuration options from the values.yaml
files under /istio/install/kubernetes/heml/subcharts directory and the
remaining configuration options like global, istiocoredns, istio_cni from
values.yaml under /istio/install/kubernetes/helm/istio directory.
* Fixes: #2136
This is a first take at a table-creating tablegen that categorizes
the output of tablegen.py. Still needed is the actual text that
goes in the description field.
* Address review comments
Mariam John
Steven Dake
Yossi Mesika