XSL Transformation very slow

[HeinrichHartmann]

On my machine the XLS transformation takes about 3sec/paper.

As we are going to apply this one to 400.000 papers, we will be waiting ~13days.
I suspect the most performance is lost by the repeated call of the java-vm

TODO: Rewrite transform.py in Java

If that does not help we might simplify the articles-data.xsl,
by removing the preprocessing of intext references.