refactor(many files): 页面部分的文件结构调整

1.views 文件夹里面分类，页面相关文件;2.公共组件全部放在components里;3.创建resources文件夹放置资源dart文件4.修改二级菜单文字大小

BREAKING CHANGE: 重构，建议删除本地db,再编译

lib/utils/example_code_parser.dart

@@ -0,0 +1,43 @@
+/*
+ * @Author: 一凨 
+ * @Date: 2019-01-14 11:42:36 
+ * @Last Modified by: 一凨
+ * @Last Modified time: 2019-01-14 16:53:11
+ */
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import '../routers/application.dart';
+import 'package:flutter/services.dart';
+import 'package:url_launcher/url_launcher.dart';
+import 'package:flutter/material.dart';
+
+
+Map<String, String> _exampleCode;
+String _code;
+
+void _launchURL(String url) async {
+  if (await canLaunch(url)) {
+    await launch(url);
+  } else {
+    throw 'Could not launch $url';
+  }
+}
+
+Future<String> getExampleCode(context,String filePath, AssetBundle bundle) async {
+  if (_exampleCode == null) await _parseExampleCode(context,filePath, bundle);
+  return _code;
+}
+
+Future<void> _parseExampleCode(context,String filePath, AssetBundle bundle) async {
+  String code;
+  try {
+    code = await bundle.loadString('lib/widgets/$filePath');
+  } catch (err) {
+    Navigator.of(context).pop();
+    _launchURL(Application.github['widgetsURL'] + filePath);
+  }
+  _code = code;
+}