Move Scala pdf to its own module

[Ana Mª Marquez]

For solving sonatype threats, we would like to move optional DSL feature to their own modules, in this case, pdf function should be moved to a module called xef-scala-pdf that depended on xef-scala, xef-tokenizer , and xef-pdf.

[Tomás Cayuelas Ruiz]

We already removed all the Scala support, so we can close this task.