v3.0.0-docker-alpha.1

v2.5.9-docker-alpha.1 migrated to eZ Platform v3.0.0 with less satisfactory parameter files (like config/packages/doctrine.yaml).

At release time, I have:

• macOS Catalina 10.15.3
• Docker for Mac Edge 2.2.3.0
  • Docker 19.03.8
  • Docker Compose 1.26.0-rc3
• Docker Containers:
  • Apache 2.4.38
    • PHP 7.3.14
  • Varnish 6.0.6
  • Redis 3.2.12
  • MariaDB 10.4.12
  • Solr 7.7.2