WebOfTrustInterface: Add getAllIdentities()

- The function is already defined at the implementation class
WebOfTrust.
- It needs to be in the interface because class persistent has a member
of the interface type, and class IdentitiesSubscription in
SubscriptionManager will have to use getAllIdentities().
WebOfTrustInterface: Add getAllTrusts()

- The function is already defined at the implementation class
WebOfTrust.
- It needs to be in the interface because class Persistent has a
member of the interface type, and class TrustsSubscription in
SubscriptionManager will have to use getAllTrusts().
WebOfTrustInterface: Add getAllScores()

- The function is already defined at the implementation class
WebOfTrust.
- It needs to be in the interface because class Persistent has a
member of the interface type, and class ScoresSubscription in
SubscriptionManager will have to use getAllScores().