Set the state of the agent
an external pointer returned by newAgent
an R list giving the components of the state to be undated.
In this framework, a state is a list, each named component is called a domain. This function only updates the values of the domain given in the "value" list, while leave the other components not in the "value" list unchanged.
If agent is an R6 object, then we should either use agent$schedule, or use schedule(agent$get, event)