MAGETWO-91802: Refund amounts are off when Rewards, Store Credit and Gift Card used

 - Added math rounding for Reward Points balance
 - Fixed Gift Card account order comments history
 - Fixed Gift Card totals block
 - Added possibility to update totals for changed Store Credit during refund

Author: YevSent

dev/tests/functional/tests/app/Magento/Sales/Test/Block/Adminhtml/Order/Creditmemo/Form/Items.php

@@ -51,6 +51,9 @@ public function getItemProductBlock($productSku)
      */
     public function clickUpdateQty()
     {
-        $this->_rootElement->find($this->updateQty)->click();
+        $button = $this->_rootElement->find($this->updateQty);
+        if (!$button->isDisabled()) {
+            $button->click();
+        }
     }
 }

dev/tests/functional/tests/app/Magento/Sales/Test/Constraint/AssertNoCreditMemoButton.php

@@ -30,7 +30,7 @@ public function processAssert(SalesOrderView $salesOrderView, OrderIndex $orderI
         $orderIndex->getSalesOrderGrid()->searchAndOpen(['id' => $order->getId()]);
         \PHPUnit\Framework\Assert::assertFalse(
             $salesOrderView->getPageActions()->isActionButtonVisible('Credit Memo'),
-            'Credit memo button is present on order view page.'
+            'Credit memo button should not be present on order view page.'
         );
     }