keep InnerException wherever appropriate

The C# Exception type offers the ability to store an InnerException which is sometimes quite helpful for debugging. Hence, wherever appropriate, any exceptions caught and rethrown should be stored into the InnerException field to provide the original error information to the caller.

The only exception (pun intended) to this is TApplicationException - this type is intended to be serialized and sent back to the client. Not only that there is no way to preserve that information, it also could compromise possibly sensitive information to clients, which is a bad thing to happen w/regard to security.