#45 add, remove, re-add packages breaks the config

[Jean-Philippe Lambert]

jMax 4.1.0-latest_cvs
redhat 7.3 (i686-Linux-2.4.18-4)
sun j2sdk1.4.1_03

When I add packages, remove them, an add then again, my jMax
config is broken (e.g. dtd and suivi).

I had to delete the default_config.jprj file for jMax to work again, and
carefully add the packages.