FCPInterface: Remove sendAllTrustValues(), not used anymore

- Was being used in
SubscriptionManager.Subscription.synchronizeSubscriberByFCP(), which has
been replaced by the recent commits which send synchronizations as
regular ObjectChangedNotifications
- Also, remove support for calling handleGetTrusts() with
request=null since sendAllTrustValues() was the only user of that
feature.
SubscriptionManager.TrustsSubscription: Use
FCPInterface.sendBeginOrEndSynchronizationNotification()

Based on the code in IdentitiesSubscription.
SubscriptionManager.ScoresSubscription: Use
FCPInterface.sendBeginOrEndSynchronizationNotification()

Based on the code in IdentitiesSubscription.
Will probably soon make this use generics to eliminate the code
duplication.