Also renamed state package "psychology.stimuli" to "psychology.perception".

Also renamed following classes:
- "EventCognition" to "StimulusProcessor"
- "SalientBehaviorCognition" to "SalientBehaviorProcessor"
- "EventController" to "StimulusController"

Watch out: Event output processors and also the existing scenario files
have not been migrated. Therefore, the unit tests fail at the moment!