sylius_product_variant table data update (FIX)

Adding an alter query to add the 2 missing sylius_product_variant columns before updating datas

Fix for this wrong pull [#1423](https://github.com/Sylius/Sylius/pull/1423)

According to this error
```
Twig_Error_Runtime: "An exception has been thrown during the rendering of a template ("Could not convert database value "" to Doctrine Type array") in "LVPWebBundle:Frontend/Product:_singleBox.html.twig"
```
sylius_product_variant table should be updated to fill the missing pricing_calculator and pricing_configuration datas.

This SQL update solve this migration problem for my project.
Merge pull request #1427 from psyray/patch-1

sylius_product_variant table data update (FIX)