Custom action for dependent resources  #851

Adding a custom action into workflow for dependent resources.

With introducing dependsOn, in the background there will be a plan created from the DAG of resources, and subsequently executed. Not everything can be modeled resource oriented way. So to be able to hook on the execution, propose a special "action dependant". (This is analogy to null resource in terraform)

This action will be executed in place, the scheduler algorithm should always wait for it synchronously, other resources could depend on it as on other resources. (There can be even output param in place)

DISCLAIMER: Create this issue is for sake of completeness. Could be implemented as the last step, and mainly after #850