Add image master filename to list of importable fields

phpcs-errors:241 phpunit-status:successful

values/availableFields.php

@@ -1070,6 +1070,16 @@ for ($i = 1; $i <= 5 * $fieldNoMultiplicator; $i++) {
             "name_human_readable" => $object['main_image'],
             "explica"             => "",
         ],
+        "image_master_filename{$i}" => [
+            "required"            => false,
+            "allowedValues"       => [],
+            "dependsOn"           => [
+                "image_name{$i}", "image_owner{$i}", "image_rights{$i}", "image_visible{$i}", "image_main{$i}"
+            ],
+            "remark"              => '',
+            "name_human_readable" => $image_incha['master_filename'],
+            "explica"             => $image_incha['master_filename_explica'],
+        ],
     ]);
 
 }