Adding nodegroup_template panel for Sahara

The nodegroup_template panel provides functionality
to define the hadoop processes and configuration of
those processes that will eventually make-up a
hadoop cluster.
This code was originally from:
https://github.com/openstack/sahara-dashboard

Change-Id: If56f69a2fbb81a0f9eed284aeab5541fa9249fb4
Partial-Implements: blueprint merge-sahara-dashboard
Co-Authored-By: Nikita Konovalov <nkonovalov@mirantis.com>
Co-Authored-By: Dmitry Mescheryakov <dmescheryakov@mirantis.com>
Merge "Adding nodegroup_template panel for Sahara"