Replace openhtmltopdf with another solution.

[jochenw]

Right now, the PdfConverterExtension depends on openhtmltopdf. Which is an unacceptable solution, because openhtmltopdf is LGPL-licensed, thus clearly contradicting the license of Flexmark itself.

Please, implement an alternative solution for rendering PDF, perhaps based on OpenPDF, iText 2.1.7, or even PDFBox itself, that can be used in license-sensitive environments.

Thanks,

Jochen