Upgrade precautions

Because laravel-admin 1.5 built-in table structure has been modified, it is recommended that you re-install laravel 5.5 and laravel-admin 1.5, and then migrate the code over

Code migration needs attention：

• Please refer to the table structure changes tables.php
• Routing file structure is modified please refer to routes.stub
• Please refer to the configuration file structure changes admin.php
• The chart component has been removed and can no longer be used, please refer to Custom chart