inbox: create InboxItemsHistory synced collection (#96)

Notesnook.API/Interfaces/ISyncItemsRepositoryAccessor.cs

@@ -38,6 +38,7 @@ namespace Notesnook.API.Interfaces
         SyncItemsRepository Colors { get; }
         SyncItemsRepository Vaults { get; }
         SyncItemsRepository Tags { get; }
+        SyncItemsRepository InboxItemsHistory { get; }
         Repository<UserSettings> UsersSettings { get; }
         Repository<Monograph> Monographs { get; }
         Repository<InboxApiKey> InboxApiKey { get; }