Enhancement for Instance Service's Reference implementation

[johannesheucher-gip]

Now

Implementing a reference Workflow requires the user to model the complete signature (including throws) inside the "Abstract" section, before he can see the desired Workflow options inside the dropdown.

Problems

• Modelling the signature inside the "Abstract" section is not intuitive (and implicitly sets the abstract flag on the data type)
• Having to model the complete signature needs much time and is not very adaptive to signature changes

Proposal

The dropdown offers all Workflows that have the owning data type as its first input (regardless of output and throws signature).
Having selected a Workflow also establishes this Service's signature (must be displayed - readonly).
We also need an "Open" button besides the dropdown to open the reference Workflow.

Sub Types

For an overridden Service, it is not possible to change the signature except for the following cases:

1. The input variables may be more general
2. The output variables may be more specific
3. The exceptions may be in a subset

For example, this has an effect for the provided reference Workflows.

[TorbenSiegismund-GIP]

A button to create a new Workflow with the correct signature next to the "Open" button could be a nice addition.