Remove special ArrayHandleMultiplexer template case

There was a special case for ArrayHandleMultiplexer where if you gave it just one type it would treat that as a value type rather than an array to support and instead provide a default list of types. However, GCC 4.8 is having trouble compiling the code to create the default list, the semantics are confusing, and the more I think about it the less likely I think we will need this functionality. So, just getting rid of that.