Delegate usage refactor

In the process of changing the resharper runner we detected that the current DelegateUsageAttribute just makes things more complicating. I simply step to a cleaner API is that we obsolete the DelegateUsageAttribute with the Enum and instead introduce an Attribute for each DelegateUsage. This pull also contains an example which provides the old and the new way. I'm using Fody.Obsolete to provide an easy machinism to deprecate the DelegateUsageAttribute for future versions. The reference to Fody is removed during compile time automatically by Fody itself.

Discussed already with @agross