Set name and url in Password non-optional

Name and url in Password class shouldn't be optional because we store
them in core data as non-optional. This change also help us to avoid
man unneccessary unwrap.

passKit/Helpers/AppError.swift

@@ -17,6 +17,7 @@ public enum AppError: Error {
     case PGPPublicKeyNotExistError
     case WrongPasswordFilename
     case YamlLoadError
+    case DecryptionError
     case UnknownError
 }
 
@@ -39,6 +40,8 @@ extension AppError: LocalizedError {
             return "Cannot write to the password file."
         case .YamlLoadError:
             return "Cannot be parsed as a YAML file."
+        case .DecryptionError:
+            return "Cannot decrypt password."
         case .UnknownError:
             return "Unknown error."
         }