Fix SyliusTaxationBundle when it's use as a standalone bundle

when i was playing with the taxation bundle i've found a bunch of issue, here are the issue i have found:

* route ``sylius_tax_category_create`` and ``sylius_tax_rate_create`` are invalid, they contains an id parameters
* some vars have not a good name such as rates instead of tax_rates and categories instead of tax_categories
* sorting don't work due to the used of the old syntax _sortable
* tax rate detail page is empty
* delete link are just link without the proper http method