Row objects and Cell styling

This commit introduces Row and Cell entities, that will replace the arrays passed in previously.
It also adds support for Cell styling (instead of Row styling only).

src/Spout/Writer/Common/Manager/WorksheetManagerInterface.php

@@ -2,7 +2,7 @@
 
 namespace Box\Spout\Writer\Common\Manager;
 
-use Box\Spout\Writer\Common\Entity\Style\Style;
+use Box\Spout\Writer\Common\Entity\Row;
 use Box\Spout\Writer\Common\Entity\Worksheet;
 
 /**
@@ -12,17 +12,15 @@ use Box\Spout\Writer\Common\Entity\Worksheet;
 interface WorksheetManagerInterface
 {
     /**
-     * Adds data to the worksheet.
+     * Adds a row to the worksheet.
      *
      * @param Worksheet $worksheet The worksheet to add the row to
-     * @param array $dataRow Array containing data to be written. Cannot be empty.
-     *          Example $dataRow = ['data1', 1234, null, '', 'data5'];
-     * @param Style $rowStyle Style to be applied to the row. NULL means use default style.
+     * @param Row $row The row to be added
      * @throws \Box\Spout\Common\Exception\IOException If the data cannot be written
      * @throws \Box\Spout\Common\Exception\InvalidArgumentException If a cell value's type is not supported
      * @return void
      */
-    public function addRow(Worksheet $worksheet, $dataRow, $rowStyle);
+    public function addRow(Worksheet $worksheet, Row $row);
 
     /**
      * Prepares the worksheet to accept data