Minor refactoring of CPController (variable guessConfidence is redundant)

Instance variable **guessConfidence** in **CPController** is only used to pass the confidence message string into **performTransitionFrom:to:** . It is more clear and straightforward to just pass that value as an extra parameter of the method.

Also, the guess' parameters (UUID and confidence value) returned from **getMostConfidentContext:** are now passed using **NSArray** -- the manipulations required to extract those two parameters from **NSDictionary** are an overkill.