improve docs

[mordamax]

In order to skip showing the "sample" example introduced an "exclude" flag to skip from docs.
We could simply delete "sample" and there's no problem but i found it useful often to check quickly that gitlab jobs with parameters work, so would prefer to keep.

• Docs:
  • support "example" field from type_rule
  • skip rendering a table with args, if there's no args (also make it not required)
  • make help/clean so they go as first basic commands in docs
  • add "excluded" to schema, so some commands could be skipped in docs