Fix Task in Studio Workflow should be able to create buttons when AppDef=WebUI

Take a LTS2017+JSF+WebUI project, go in graph and create a workflow task:
6 tabs shown
Take a LTS2017+WebUI project, go in graph and create a workflow task:
4 tabs shown
=> The ability to create choices for the user actions is currently lost in WebUI

It is expected to be able to add buttons on demand in the task definition.

TODO
When Web UI dependency is added, show the resolution actions tab