Restrict visibility of implementations constructors

The intended usage pattern for the library is to create the implementations using the `TableRepository.Create` or `TablePartition.Create` factory methods.

The implementations are public so that if a consumer wants to inherit them and provide different defaults for the constructors, they can do that, but users should not be instantiating the implementations directly.

For DI scenarios, the factory method can be used to provide instances, or a such a derived generic class providing default values for the lambdas that are hard to inject (the `Func<T, string>` for partitionKey and rowKey) can be used instead.

Fixes #14

Author: kzu

src/TableStorage/TablePartition`1.cs

@@ -19,7 +19,7 @@ partial class TablePartition<T> : ITablePartition<T> where T : class
         /// </summary>
         /// <param name="storageAccount">The storage account to use.</param>
         /// <param name="tableName">Optional table name. If no value is provided, <see cref="DefaultTableName"/> will be used.</param>
-        public TablePartition(CloudStorageAccount storageAccount, string tableName, string partitionKey, Func<T, string> rowKey)
+        protected internal TablePartition(CloudStorageAccount storageAccount, string tableName, string partitionKey, Func<T, string> rowKey)
         {
             TableName = tableName ?? TablePartition.GetDefaultTableName<T>();
             PartitionKey = partitionKey ?? TablePartition.GetDefaultPartitionKey<T>();

src/TableStorage/TableRepository`1.cs

@@ -28,7 +28,7 @@ partial class TableRepository<T> : ITableRepository<T> where T : class
         readonly Func<T, string> rowKey;
         readonly AsyncLazy<CloudTable> table;
 
-        public TableRepository(CloudStorageAccount storageAccount, string tableName, Func<T, string> partitionKey, Func<T, string> rowKey)
+        protected internal TableRepository(CloudStorageAccount storageAccount, string tableName, Func<T, string> partitionKey, Func<T, string> rowKey)
         {
             this.storageAccount = storageAccount;
             TableName = tableName ?? TableRepository.GetDefaultTableName<T>();