[OrderBundle] Fixed #1187. Don't generate order number if it already exists

This fixes #1187 - order number should not be re-generated if it's already assigned
Merge pull request #1311 from boskee/duplicate-order-number-fix

[OrderBundle] Fixed #1187. Don't generate order number if it exists
[CartBundle] Removed redundant cart refresh

Cart refresh is already handled by RefreshCartListener which subscribes to SyliusCartEvents::CART_CHANGE. That event is already dispatched along cart-changing events such as SyliusCartEvents::ITEM_REMOVE_INITIALIZE and therefor refreshCart() should be removed from CartListener
Added Order helpers to clear adjustments (with specs)
Merge pull request #1322 from boskee/remove-extra-refresh

[CartBundle] Removed redundant cart refresh
Merge pull request #1323 from elliot/feature/order-helpers

[OrderBundle] Add helpers to clear adjustments