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-samples/src/main/resources/application.yml

@@ -8,6 +8,8 @@ spring:
     history:
       name: spring-shell-samples-history.log
     command:
+      help:
+        grouping-mode: group
       completion:
         root-command: spring-shell-samples
 ## disable console logging