Add customizations for cloudsearchdomain command

* Rename --query to --search-query to avoid shadowing our --query arg
* Add validation to require --endpoint-url when using cloudsearch domain
  commands.
Update changelog with latest changes
Bumping version to 1.3.20
Merge branch 'release-1.3.20' into develop

* release-1.3.20:
  Bumping version to 1.3.20
  Update changelog with latest changes
  Add customizations for cloudsearchdomain command