Added ability to modify my.cnf using config.yml

[kducharm]

Description

Docker settings do not allow for custom configuration to be applied by a client. Some parameters of my.cnf may need to be modified and are replaced when updating a client's repo. This adds a docker configuration section in config.yml

QA Tests

• [x] Check out branch locally
• [x] ahoy site up
• [ ] Check variable:

  ahoy docker exec bash
  drush --root=docroot sqlq "show variables like 'innodb_file_format'"
  exit

  should be Antelope

• [x] Modify config/config.yml:

  docker:
  mysql_cnf:
  mysqld: #[mysqld] section in my.cnf
    - "innodb_large_prefix=on"
    - "innodb_file_format=Barracuda"

• [x] ahoy docker stop ahoy docker up ahoy build config
• [ ] Check variable:

  ahoy docker exec bash
  drush --root=docroot sqlq "show variables like 'innodb_file_format'"
  exit

  should be now Barracuda

[dafeder]

Closing; may address with DKAN Tools if need arises.