Implement command alias only for methods

[roumcha]

Problems

CommandAttribute has a constructor with multiple names (hereinafter called aliases), but it still has some problems. I guess that's the reason it's not officially introduced in readme.md.

1. Aliases are shown twice in command helps (related to #96)
2. Aliases doesn't work for classes
3. If [2] above got solved, command help messages would be hard to read.

An example for [3]

code: ```csharp [Command(new[] {"class1", "class2"})] class App : ConsoleAppBase { [Command(new[] { "command1", "command2" }, "desc")] public void Sample() { Console.WriteLine("Hello!"); } } ``` The help text for the code above would be: ```text class1, class2 command1, command2 desc ``` It's hard to see which is the parent's name and which is the method's at a glance.

What this PR will do

To solve [1] and [3], this PR will:

• not show aliases in command list in help messages

• add "Aliases: ..." line to the help text for commands which have aliases

$ myapp.exe command-name --help 
Usage: command-name

Print "Hello, world!"

Options:
  ()

Aliases: command-alias-1, command-alias-2

• add tests for these changes

What this PR won't do:

• Fix the problem [2]: It was hard for me to fix it.

[roumcha]

The diff is very large because ConsoleAppEngine.cs had a lot of LF, and I accidentally changed them all into CRLF... Would it be better to recreate my commits?

[github-actions[bot]]

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