Removed generic argument from TableHelperExtensionMethods.FillInstance()

TableHelperExtensionMethods.FillInstance() has been updated to remove the generic argument "T" and instead rely on the runtime type of the instance parameter that is passed in (instance.GetType()).

The problem with the generic argument T is if an instance of a subtype of T is passed to the method, that subtype's properties will not be populated. Only the properties defined on T are considered. This places a considerable limitation on populating instances of class hierarchies.

Unfortunately, this will break client that invoke FillInstance() with the generic argument explicitly defined; however, those who have not supplied the argument will compile fine.