ODS writer

Added ODS writer
Refactored XLSX writer to abstract some pieces into an abstract multi-sheets writer
Created an abstract style helper
Moved shared components around

src/Spout/Common/Escaper/ODS.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Box\Spout\Common\Escaper;
+
+/**
+ * Class ODS
+ * Provides functions to escape and unescape data for ODS files
+ *
+ * @package Box\Spout\Common\Escaper
+ */
+class ODS implements EscaperInterface
+{
+    /**
+     * Escapes the given string to make it compatible with XLSX
+     *
+     * @param string $string The string to escape
+     * @return string The escaped string
+     */
+    public function escape($string)
+    {
+        return htmlspecialchars($string, ENT_QUOTES);
+    }
+
+    /**
+     * Unescapes the given string to make it compatible with XLSX
+     *
+     * @param string $string The string to unescape
+     * @return string The unescaped string
+     */
+    public function unescape($string)
+    {
+        return htmlspecialchars_decode($string, ENT_QUOTES);
+    }
+}

src/Spout/Common/Type.php

@@ -8,6 +8,7 @@ namespace Box\Spout\Common;
  */
 abstract class Type
 {
-    const CSV = "csv";
-    const XLSX = "xlsx";
+    const CSV = 'csv';
+    const XLSX = 'xlsx';
+    const ODS = 'ods';
 }