Fix Shipping discount with percentage

Shipping discount with percentage must be calculated after shipping selection.
Use getAlias
Add symfony/expression-language as dependency
The methods should be after the attributes
Merge pull request #1057 from aRn0D/method-order

The methods should be after the attributes
Merge pull request #1052 from umpirsky/fix/variable-product-repository-alias

Use getAlias
dispatching variant creation event
Merge pull request #1053 from abimus/fix/expression-language-deps

[ResourceBundle] Add symfony/expression-language as dependency
Merge pull request #1051 from ramol/master

Fix Shipping discount with percentage
Remove final keyword in SyliusCheckoutEvents.

I want to extend and add more events.
Include promotion total to PayPal gateway.
Set shipment state to onhold before process payment.
fixed spec
Merge pull request #1060 from kayue/patch-5

Remove final keyword in SyliusCheckoutEvents.
Merge pull request #1063 from kayue/patch/order-shipping-state

Set shipment state to onhold before process payment.
Merge pull request #1059 from akovalyov/fix/generator-events

Proper dispatching of variant creation event
Merge pull request #1062 from kayue/patch-6

[BUG] Include promotion total to PayPal gateway.
Resource bundle depend on symfony form.
Merge pull request #1069 from aRn0D/composer

Resource bundle depend on symfony form.
Testing must take place in the en-US locale since tests are written for it.
This solve the behat failures for checking promotional discounts (most locales
show negative number as: -$100.00,  en-US shows ($100.00)
Fixes #853 along with other issues.