PJSIP .net wrapper with high level API

PJSIP is wrapped in an unmanaged DLL using swig - https://github.com/StrikeForceZero/PJSip-CSharp built using visual studio 2008 to acquire true .net 2.0 compatiblity

currently the SDK uses 4.0 but can be ajdusted to work with 3.5 possibly even 2.0 with enough porting.

This project is still in its early form and has a lot of refactoring/cleanup to be done It's currently being used in a production enviroment with minimal/no issues

Method names and properties are subject to change.

Pull requests welcome.