Feature request: FlyingSaucer could generate BarCode on the fly

[asolntsev]

As shown in #444:

when FS encounters such an image in html:

<img th:src="PR12345678" type="code128" style="height: 100px"/>

it could replaced it by generated BarCode.

Basically, we need to add BarcodeReplacedElementFactory from #444 to FS codebase.