v0.5.7 Nuget release

What's Changed

• Fixes for missing dependnacy issue and Object Not found issue when updating a field to a null value by @MattB-msft in #182

Full Changelog: 0.5.5...0.5.7

Removed Sealed attribute from the Service Client Class.
Fixed an issue with null values being sent to the API causing a null exception to be raised. Fix for #175 fix for #180 fix for #179
Fixed missing nuget dependency for Microsoft.Identity.Client.Extensions.Msal, Nuget now properly includes that package.