Add Elasticsearch 5.x and MySQL 5.7 to compose files

[damien-carcel]

Akeneo master branch now requires PHP 7.x with PHP-FPM, MySQL 5.7 and Elasticsearch 5.x. MongoDB is no longer used.

The actual Apache compose file will be kept for Akeneo 1.7 and previous, with mod_php 5.6, MySQL 5.5 and MongoDB 2.4 by default.

• For Akeneo master (next version to come):
  • Remove MongoDB
  • Set MySQL to 5.7 (add specific configuration)
  • Add Elasticsearch 5
  • Use carcel/akeneo-fpm:php-7.1
  • Document those changes

See issue #224.