107.0.0-preview.1

First preview release using HttpClient.

This release includes major breaking changes:

• Interface IRestClient is removed, use RestClient class instead
• Interface IRestRequest is removed, use RestRequest class instead
• Interface IRestResponse is removed, use RestResponse class instead
• Most of the client options are now in RestClientOptions as they can't be changed after creating the HttpMessageHandler instance
• All synchronous methods are gone, use asynchronous methods instead
• Default JSON serializer is now using System.Text.Json, SimpleJson is gone
• Support for .NET 4.5 is removed, for legacy .NET Framework use the .NET Standard package