Update process compiler

[antho1404]

Update the compiler to the latest version:

• Remove trigger field
• Rename tasks to steps
• Include different types of node (filter, trigger, task)

Example of format:

key: Event
steps:
  - type: trigger
    key: trigger
    instance: 
      src: ../serviceA
      env:
        - FOO=BAR
    eventKey: eventX
  - type: filter
    conditions:
      message: event
  - type: task
    key: execute-task-x
    instance:
      src: ../serviceA
      env:
      - FOO=BAR
    taskKey: taskX
    inputs:
      message:
        stepKey: trigger
        key: message
  - type: task
    key: toTaskY
    instance:
      src: ../serviceB
    taskKey: taskY
    inputs:
      inputA:
        stepKey: execute-task-x
        key: xxx

[NicolasMahe]

If stepKey of an input is empty, the compilation should set it to the previous node/step.

[antho1404]

Did the update. This adds a bit more complex because we don't want to take the previous node but the previous node that has data (all except the filter)