Updated the InterfaceDescription for the Unity Extension

Updated the GetHashCode function to return a hash based on the
contents of the InterfaceDescription

Additional Methods:
   - InterfaceDescription.AddMethod
   - InterfaceDescription.GetMethod
   - InterfaceDescription.GetSignal

Unit tests added for
   - InterfaceDescription.GetMembers
   - InterfaceDescription.AddMethod
   - InterfaceDescription.GetMethod
   - InterfaceDescription.HasMember
   - InterfaceDescription.GetProperties
   - InterfaceDescription.GetSignal
   - InterfaceDescription.Equals
   - InterfaceDescription.operator==
   - InterfaceDescription.GetHasCode

Additional Whitespace and documentation changes.

Change-Id: If3c8384b60e7de7a8b7182eb35e246d07cb569c3