[WIP] Added PauseNodeAction

Added PauseNodeAction as a way of marking a node as being a node that causes the run to pause/suspend execution.

I think it might make sense to add a start and end time to this in case the node was not paused for the full duration of it's execution?
Cool... I was wondering about that actually and meant to add it as a comment in the PR description.

When wondering about this I was also wondering what was the logic behind where the different Action impls are located... some in api, some in step-api, some in basic-steps, support etc.