The part of the system that makes up the agents.
Every agent is a unit with some freedom. It has a notion of who it is
and it has its own plans. The most significant constituents of an
agent are:
A Reactor, embodying the reactive system and mapping plans
to behaviors.
A RobotSpec containing mappings from robot parameters to
values.
A Planner embodying the deliberative system, wrapped in a
PlannerControl object to make it easier to switch planners. Unless changed, the planner used will be NullPlanner (that does nothing).