Move Documentation to new Drupal 8 Docs

Problem/Motivation

The old Site Builders Guide is moving to the new documentation system.
from https://www.drupal.org/documentation/build →
to https://www.drupal.org/docs/extending-drupal/contributed-modules →

Proposed resolution

Migrate the documentation pages from the site building guide:
https://www.drupal.org/node/2648186 →

Update as needed

Update documentation links on the module page