Removed hasPassedExactly assertion, because of not strictly enough defined semantics.

(Assertion 'hasPassed' imho makes sense for activityIds, while 'hasPassedExactly' binds the verification too close to internal execution details of the process engine, like e.g. treating merging gateways as ActivityInstances - or not. Forthcoming assertions will focus on verifying execution semantics mainly with respect to tasks. In the case of tasks 'exact' assertions will make much more sense.)
Removed unused messageEventDefinition. Example process is actually started by key.