Rework help command

- Change help command output to get templated using
  model classes.
- Remove things around ParameterDescription as those are
  replaced with template classes.
- Fixes for native configs.
- For now availability and aliases are removed from
  help to get back in better form.
- Aliases has been partly introduced to structure.
- Fixes #422

spring-shell-docs/src/main/asciidoc/using-shell-components-builtin.adoc

@@ -9,56 +9,77 @@ However, if they are not overridden or disabled, this section describes their be
 [[help-command]]
 ===== Help
 
-Running a shell application often implies that the user is in a graphically limited
-environment. Also, while we are nearly always connected in the era of mobile phones,
-accessing a web browser or any other rich UI application (such as a PDF viewer) may not always
-be possible. This is why it is important that the shell commands are correctly self documented, and this is where the `help`
-command comes in.
+Running a shell application often implies that the user is in a graphically limited environment. Also, while we are
+nearly always connected in the era of mobile phones, accessing a web browser or any other rich UI application
+(such as a PDF viewer) may not always be possible. This is why it is important that the shell commands are correctly
+self documented, and this is where the `help` command comes in.
 
 Typing `help` + `ENTER` lists all the commands known to the shell (including <<dynamic-command-availability,unavailable>> commands)
 and a short description of what they do, similar to the following:
 
 ====
-[source]
+[source, bash]
 ----
-shell:>help
+my-shell:>help
 AVAILABLE COMMANDS
-        add: Add numbers together.
-      * authenticate: Authenticate with the system.
-      * blow-up: Blow Everything up.
-        clear: Clear the shell screen.
-        connect: Connect to the system
-        disconnect: Disconnect from the system.
-        exit, quit: Exit the shell.
-        help: Display help about available commands.
-        register module: Register a new module.
-        script: Read and execute commands from a file.
-        stacktrace: Display the full stacktrace of the last error.
 
-Commands marked with (*) are currently unavailable.
-Type `help <command>` to learn more.
+Built-In Commands
+       exit: Exit the shell.
+       help: Display help about available commands
+       stacktrace: Display the full stacktrace of the last error.
+       clear: Clear the shell screen.
+       quit: Exit the shell.
+       history: Display or save the history of previously run commands
+       completion bash: Generate bash completion script
+       version: Show version info
+       script: Read and execute commands from a file.
 ----
 ====
 
 Typing `help <command>` shows more detailed information about a command, including the available parameters, their
 type, whether they are mandatory or not, and other details.
 
-The follwoing listing shows the `help` command applied to itself:
+The following listing shows the `help` command applied to itself:
 
 ====
+[source, bash]
 ----
-shell:>help help
-
-
+my-shell:>help help
 NAME
-	help - Display help about available commands.
+       help - Display help about available commands
 
-SYNOPSYS
-	help [[-C] string]
+SYNOPSIS
+       help --command String
 
 OPTIONS
-	-C or --command  string
-		The command to obtain help for.  [Optional, default = <none>]
+       --command or -C String
+       The command to obtain help for.
+       [Optional]
+----
+====
+
+Help is templated and can be customized if needed. Settings are under `spring.shell.command.help` where you can use
+`enabled` to disable command, `grouping-mode` taking `group` or `flat` if you want to hide groups by flattening
+a structure, `command-template` to define your template for output of a command help, `commands-template` to define
+output of a command list.
+
+If `spring.shell.command.help.grouping-mode=flat` is set, then help would show:
+
+====
+[source, bash]
+----
+my-shell:>help help
+AVAILABLE COMMANDS
+
+exit: Exit the shell.
+help: Display help about available commands
+stacktrace: Display the full stacktrace of the last error.
+clear: Clear the shell screen.
+quit: Exit the shell.
+history: Display or save the history of previously run commands
+completion bash: Generate bash completion script
+version: Show version info
+script: Read and execute commands from a file.
 ----
 ====