Added ability for delegate to handle ubiquity becoming unavailable.

[ADDED]     ubiquityStoreManagerHandleCloudDisabled: in delegate.
[UPDATED]   Make cloudAvailable directly dependant on _currentIdentityToken and avoid ubiquityIdentityToken in favor of _currentIdentityToken.
Merge branch 'master' of github.com:lhunath/UbiquityStoreManager
Don't crash on enumerateCloudStores if iCloud is disabled.

[FIXED]     Crash on enumerateCloudStores when there is no cloud URL.
A small fix to avoid a possible crash.
I am resigning maintenance of this project for now due to time constraints.
Merge branch 'master' of github.com:lhunath/UbiquityStoreManager