Header interface() should include Name() 

The [Header interface](https://github.com/moov-io/iso8583/blob/679e5a69f86ddb79dc0e35f61a0c1ad8dcfaf064/network/header.go#L59) should include a Name() property like [Specs](https://github.com/moov-io/iso8583/blob/679e5a69f86ddb79dc0e35f61a0c1ad8dcfaf064/specs/spec87ascii.go#L13) do.  You can then switch and check which compiled header you are working with. 