Provide the Abliity to Extend Activities for Workflow Designer

Define the data information of Extend Activities, include java task, script task and rest task.

Define the APIs for query the  Extend Activities.

WF Designer UI load the Extend Activities.

Support using the Extend Activities to design a new workflow.

Save the workflow with Extend Activities.

Convert Extend Activities to standard bpmn activities.

Ganerate bpmn file with Extend Activities.