Reimplement Cron Trigger in DSL v2

We need to implement Cron Trigger in DSL v2.

Suggested syntax:

Trigger DSL example 1:

  trig1:
    type: periodic
    parameters:
      cron-pattern: "*/1 * * * *"
    workflows:
        - wf1:
            input:
                # Regular map (heavy syntax)
        - wf2 param1=val1 param2=val2 task_name='task1' # Short syntax
    actions:
        # The same for actions

Trigger DSL example 2:

  trig1:
    type: periodic
    parameters:
      cron-pattern: "*/1 * * * *"
    workflows: ["wf2 param1=val1 param2=val2 task_name='task1'", ...] # YAML parser easily digests it
    actions: # same for actions