Updated REST API documentation

* Removed old rest api samples from etc dir
* Updated res_api_v1.0 and v1.1 pages with actual state of Sahara and its
  api
  - list of plugins shows more plugins - 'vanilla,spark,hdp,cdh'
  - image examples work with latest image with vanilla 2.4.1
  - updated node-group templates and cluster templates  examples with
    2.4.1 node-processes
  - updated cluster related ops in docs
  - edp ops looks correct and clear, nothing to change
  - removed rest-api-samples dir both for cluster and edp ops

Implements blueprint: move-rest-samples-to-docs

Change-Id: I158549bf8fda383e1b3356b7751e28c9f83f8598
Merge "Updated REST API documentation"