OP-556 - Adding Sylius 2.0 support

[tomkalon]

Behat

• Changed require-dev mink-selenium2-driver version
• Changed validator css style from: .sylius-validation-error to .invalid-feedback

11 scenarios (11 passed)
127 steps (127 passed)

PHPSpec

9 specs
37 examples (37 passed)

ECS fixes

Plugin files update

• Updated plugin routes and Crud paths
• Updated icon names
• Updated twig files
• Added sample exporter - (Frank Martin) and test it

Added Sylius 2.0 support

• Updated composer.json

• Updated packege.json and webpack.config.js
  --- added Stimulus controller
  --- updated webpack.config.js, assets path and added product-entry.js

• Updated bundles.php

• Updated routes

• Updated Kernel.php

• Updated configs - removed unnecessary files and
  --- updated security.yaml
  --- added mailer.yaml