Output FOP and XEP version (with option -version)

[tomschr]

As FOP (and XEP) can have different versions, I think it is very useful to have them printed when -v is active.

The following commit adds an additional line in the output (see "FORMATTER VERSION"):

        DAPS VERSION: @PACKAGE_VERSION@
[...]
       PDF FORMATTER: fop
   FORMATTER VERSION: FOP Version 2.2
   FORMATTER WRAPPER: /local/doc/daps/libexec/daps-fop
    FORMATTER CONFIG:

@fsundermeyer I'm not sure if this is the correct style, so please review. Thanks!