Derive mode from DSN function

- Add headers in all files
- Minor field name changes

src/Mapper/CountMapper.php

@@ -1,4 +1,10 @@
-<?php declare(strict_types=1);
+<?php
+/**
+ * @author Daniel J. Summers <daniel@bitbadger.solutions>
+ * @license MIT
+ */
+
+declare(strict_types=1);
 
 namespace BitBadger\PDODocument\Mapper;
 
@@ -7,9 +13,7 @@ namespace BitBadger\PDODocument\Mapper;
  */
 class CountMapper implements Mapper
 {
-    /**
-     * @inheritDoc
-     */
+    /** @inheritDoc */
     public function map(array $result): int
     {
         return (int) $result[0];