Add short application description under name on all help screens

Currently if I type application name help screen does not contain any short description of application. If I use help on windows dir command:
```
`C:\Users\Example>dir /?
Displays a list of files and subdirectories in a directory.

...help text continues
```
I think that it's nice way of communicating for user, what this tool does (in few words).

Current output:
```
>MyApp.exe
MyApp 1.0.0
Copyright (C) 2018 MyApp

verb1 Help text for verb 1
verb2 Help text for verb 2
help Display more information on a specific command.
version Display version information.
```

Would be nice output:
```
>MyApp.exe
MyApp 1.0.0
Utility for mass renaming files
Copyright (C) 2018 MyApp

verb1 Help text for verb 1
verb2 Help text for verb 2
help Display more information on a specific command.
version Display version information.
```

I think System.Reflection.AssemblyDescriptionAttribute would be good source of this description.

首先跟踪应用程序的顶层帮助屏幕是如何组装的，以及应用程序名称、版本和版权信息写入的位置。检查那里是否可以使用 System.Reflection.AssemblyDescriptionAttribute 作为描述来源。完成的标准是：简短描述显示在所有相关帮助屏幕的名称下方，同时不影响现有的命令帮助和版本帮助。

由索引模型根据 Issue 内容生成。