Hygenic error handling and validation for pipelines

[Licenser]

Describe the problem you are trying to solve

With pipelines, we have now the chance to know what ports exist so we can guard against sending to unknown ports and errors at compile time

Describe the solution you'd like
The pipeline

define pipeline test
pipeline
  select event form in into out/something_not_defined;
end

should not compile.

At the same time this does apply to troy:

# ...
  define pipeline test
  into fancy
  pipeline
    select in into out/fancy;
  end;
#...
  connect /pipeline/test/not_fancy to /connector/stdio;