Flow improvements

[nicosammito]

• Better Suggestion Menu UI / UX
• ReferenceValue currently broken
• Missing option to adjust input and return Types

[nicosammito]

For the missing input and return types, we need a separate input component, which takes in a datatype as default value and which is capable of adding / updating / removing rules to the datatype. You should also be able to select datatypes. So maybe we need to adjust suggestion algorithm for values. But this should be fairly easy.