Reimplement unrequired/required feature. Make SimpleDependency validate only if not unrequired.
Also, check only for dependency missing for now.
Fix bug at StartingServiceTasks.create: taskDependencies parameter must be always be taken into account
Remove anti features from dependencies: there is no need for satisfied field, dependency available notifications with up parameter, and related code features.
At ServiceController removal, make remove task dependent on completeTransitionTask.
Do not invoke stop on failed services.
At SimpleDependency, only add demand after service has been installed. Otherwise, we risk demanding a registry for a dependency that won't be installed.
Force rollback of transactions with validation problems. Update tests.