This is now closer to the according TransitionEvent of lifecycle_msgs,
which includes the start_state and goal_state of a transition.

Signed-off-by: Arne Nordmann <arne.nordmann@de.bosch.com>

* Adds caching of latest reported states/modes of all systems
* Adds infer_transitions method that compares currently inferred
states/modes to cached ones and returns transitions, if detected

#42

Signed-off-by: Arne Nordmann <arne.nordmann@de.bosch.com>

Signed-off-by: Arne Nordmann <arne.nordmann@de.bosch.com>

Mode manager is now publishing transitions that are inferred by the mode
inference, i.e. state and mode transitions of systems, mode transitions
of nodes.
State transitions of nodes don't have to be published as lifecycle nodes
do this on their own.

#42

Signed-off-by: Arne Nordmann <arne.nordmann@de.bosch.com>