Run composer scripts in Dockerfile

Fix dockerfile alternate paths

Remove ./ relative path notation which doesn't work on latest version of Docker + Compose

See: https://docs.docker.com/compose/compose-file/#dockerfile

Minor enhancements for php Dockerfile

Fix PHP-CS-Fixer config

Update admin

Fixed docker for Windows

Revamp the docs

Fix assets:install command for Docker in composer.json

Use the cached mode for some Docker volumes

Use scanelf to detect runtime deps

Bump deps. Downgrade to Postgres 9.6.

Upgrade Flex