Duplicated HttpCoreDiagnosticSourceListeners  #848

There are 2 different HttpCoreDiagnosticSourceListeners.cs files.

https://github.com/Microsoft/ApplicationInsights-dotnet-server/blob/develop/Src/DependencyCollector/Shared/HttpCoreDiagnosticSourceListener.cs

and

https://github.com/Microsoft/ApplicationInsights-dotnet-server/blob/develop/Src/DependencyCollector/Shared/Implementation/HttpCoreDiagnosticSourceListener.cs

The duplicate was presumably introduced in dc8dfc6#diff-4f1ffbdf34be32bff51fcc9812e0c990

As a result #723 is not fixed (and may be some other issues as well)