Port new CosmosDB Partitioned Storage from C#

[garypretty]

A new Cosmos DB storage implementation which utilizes the v3 API and handles the partition key internally has been implemented in C#, which needs adding to the JS library.

C# implementation is here microsoft/botbuilder-dotnet#2613

[garypretty]

@mdrichardson We have had a C# code review from Chris Anderson (new to our team, formerly Cosmos). Our implementation looks great, but the recommendation is to use ReadItem as opposed to Query. I will make the change in C#, but wanted to give you the heads up.