Workflow editor: Option to open the payload browser in a task configuration pane

[msonsma]

A task edit pane now shows three options for each parameter value: [input], [workflow], [custom].

It should be extended with a fourth option: [Payload] that opens the payload browser ( as available in the swimlane mode ) showing the actual payload available based on the last run. If no payload is available - for instance when you added a new task - it should show the first available payload up-stream  Double clicking a node in the payload browser should insert the full path of that node in the field/cursor location.

The option to open the payload browser should not be limited to a task's parameter fields only; it should be available on each task's field in which payload fields can be referenced. 

Benefits:

- Clear view of payload nodes/variables available for a task 

- Clear indication of what kind of data is stored under the nodes

- No case typos in node names as you can select them in the payload browser

- Quicker developing of workflow as you don't have to switch back and forth between the workflow edit mode and the swimlane mode.

- Quicker developing of workflow even in de swimlane mode as you don't have to close the (instance/workflow instance) task configuration box in order to a) move it out of the way as it can overlap the payload pane and/or b) expand a node in the payload pane.