Csharp Device Client

• Added support for .Netstandard 1.3 for the Device SDK. Please note that is in “preview” state.
• Added messaging with x509 cert e2e tests
• Added method and twin with graceful connection shutdown e2e tests
• Fixed setting server address on mqtt for .Netstandard 1.3 build

Csharp Device Shared

• Added support for .Netstandard 1.3 for the Device Shared SDK. Please note that is in “preview” state.