[.NET SDK] Add JSONConverter to support builtin.datetimeV2.* LUIS entities

[ejadib]

This PR is intended to fix issue #2764.

FYI @msft-shahins @chrimc62

[willportnoy]

@ejadib there can be more than one meaningful item - can you update the pull request to deserialize all of them into a list of some type (e.g. IDictionary<string, object>)?

Is there a method to have newtonsoft deserialize JArray into List?

[nwhitmont]

@ejadib Any updates on the LUIS datetime v2 progress?

[pcostantini]

Hi @willportnoy , @nwhitmont .
The PR is now updated to also resolve entity's resolution multiple values

Regards,
-PabloC.

[garypretty]

Is this in the latest NuGet Bot Builder package now? If so do you have a code sample of how to use it to simply get a date value out of an entity?

[ejadib]

I created a set of extension methods to extract the values https://github.com/ejadib/LUIS-DateTimeV2-Extensions