Better (more private...) error handling

src/common.js

@@ -1,12 +1,15 @@
 'use strict';
 
 import * as fs from 'fs';
-import * as path from 'path';
 import Manifest from './Manifest.js';
 import Sequence from './Sequence.js';
 import Canvas from './Canvas.js';
 import Image from './Image.js';
 import ManifestMetadata from './Metadata.js';
+
+/**
+ * @namespace Common
+ */
 const Common = {};
 
 const authors = {
@@ -103,6 +106,8 @@ Common.getParamsFromFolders = async function() {
 /**
  * @param {string} manifestId 
  * @returns {string[]}
+ * @throws `readdir` will thrown an ENOENT error if the images folder doesn't exist.
+ * 	       The manifest route should catch it.
  */
 Common.getImageList = async function (manifestId) {
 	// Regex to exclude images with certain patterns in filename