Allow pausing action executions

[fho]

Implement a command to pause/resume the execution of actions.

Events would still be registered as normal and added to the event-queue, the event queue would not process any actions when it's paused.

This can be usefull when goordinator is used to trigger CI jobs and the CI server should be maintained. During the maintenance period it might not be able to process trigger-actions.
To not loose any events, action processing could be pause in goordinator during that period.