AlignedBuilder needs finer controls

[samuelwilliams]

Change AlignedBuilder around so that you can have some finer control on how things are done. As I said before, AlignedBuilder is designed around my arbitrary opinions, but it would be good if developers can add their own specialised handlers into the builder. This would be a BC-breaking change, but can be shipped with v4. I envisaged something like:

function myTxtHandler(Rdata\TXT $txt): string {
     //return text that is cut down into smaller chunks.
}

$builder = new AlignedBuilder();
                        //(string $type,  callable $renderer)
$builder->setRdataRenderer('TXT', 'myTxtHandler');

Originally posting in PR #83

[samuelwilliams]

PR #87