Experimenters define number of transition participants: 2pts

[skleinfeldt]

User story:

As an experimenter I can specify a property defining the number (max 8) of additional players needed to make the transition on the object. The first participant needs to be on the target, and the other participants need to be on squares adjacent to the target to activate the transition.

• Add transition level configuration for number of participants required
• Add validation in experiment transition handler to ensure required number of players in adjacent squares