Support ocropus 0.6

[jwilk]

Issue reported by @donbex:

I just installed ocrodjvu (v 0.7.13) and ocropus (v 0.6) on my system (running ArchLinux), but ocrodjvu doesn't seem to find the OCR engine.

By the little I can glimpse from the ocodjvu source, it is looking for an executable named ocroscript, which doesn't seem to be provided by ocropus, at least from version 0.5.

[jwilk]

Comment submitted by @jsbien:

Looks like ocropus has been replaced by ocropy, cf. e.g cistern.cis.lmu.de/ocrocis/tutorial.pdf.