Consider renaming `Status` enums to avoid clashes

[vpavic]

The project contains 2 enums named Status:

• com.apple.itunes.storekit.model.Status
• com.apple.itunes.storekit.verification.Status

This is unfortunate because if one needs to use both in the same class, one has to be referred to with fully-qualified class name.

Perhaps these enums could be renamed to be more specific (for example, SubscriptionStatus and VerificationStatus)?

[alexanderjordanbaker]

Resolved in #59