New endpoints, full framework targetting, bugfixes!

This release provides the following improvements:

• The NuGet package can now target the full framework again. This is useful incases where the .net core sdk has not been installed, and older versions of Visual Studio.
• Template Alias support
• The "headers" collection passed to a outbound message constructor is now used when sending messages.
• Redundant To, Cc, Bcc classes have been replaced with a Recipient class when listing outbound messages.

Thanks to all the people that reported issues or submitted pull requests!