Usage help has wrong order of options and commands

[AndreGleichner]

Describe the bug
Generated usage help is e.g.
Usage: mytool [options] [command]
instead of:
Usage: mytool [command] [options]

To Reproduce
Steps to reproduce the behavior:

1. Using this version of the library '2.4.2'
2. Run code below
3. With these arguments '-h'
4. See wrong output "Usage: mytool [options] [command]"

Expected behavior
It should show "Usage: mytool [command] [options]"
Since having any options in front of the command verb fails.

Additional context
Repro code:

    [Command("mytool")]
    [Subcommand(typeof(MysubCommand))]
    class Program
    {
        static int Main(string[] args) => CommandLineApplication.Execute<Program>(args);
    }
    [Command]
    class MysubCommand { }

As a workaround I currently have a specialized DefaultHelpTextGenerator with overridden GenerateUsage().

[natemcmaster]

Seems like an easy one to fix if you're interested in contributing a change.

[AndreGleichner]

See #308