Merge for Shivani's node-before and node-after work.

Merge commit '7a3e590aa3e0d9ba85c9ef1694c399397b4a1b94'

* commit '7a3e590aa3e0d9ba85c9ef1694c399397b4a1b94':
  Added a join the community link with instructions on basic steps.
  redundant code from AbstractNodePositionalCheckEvaluator removed
  Apache License header added to new files
  runtime functions implemented for op:node-before op:node-after