Make grouping configurable in build-in help

[jvalkeal]

• New option spring.shell.command.help.grouping-mode which can be either flat/group.
• Build-in help command can now choose if to group command or just show flat list.
• Fixes Change or remove group of "Built-in Commands" #347

[jvalkeal]

This would result for example:

AVAILABLE COMMANDS

  completion bash: Generate bash completion script
  help: Display help about available commands.
  history: Display or save the history of previously run commands
  script: Read and execute commands from a file.
  version: Show version info
  dependencies: List supported dependencies
  info: Show the Initializr server being used
  init: Initialize project

vs.

AVAILABLE COMMANDS

Built-In Commands
        completion bash: Generate bash completion script
        help: Display help about available commands.
        history: Display or save the history of previously run commands
        script: Read and execute commands from a file.
        version: Show version info

Initializr Commands
        dependencies: List supported dependencies
        info: Show the Initializr server being used
        init: Initialize project