Binary patched class files added to the "classes" folder end up in /etc

Our initial goal for creating the link /usr/lib/xwiki/WEB-INF/classes -> /etc/xwiki/classes was to be able to easily access the logback.xml logging configuration file from the same place where all the other XWiki config files are linked (i.e. /etc.xwiki/).

However, in the current implementation, when we start adding patched java .class files to /usr/lib/xwiki/WEB-INF/classes, those files actually end up in /etc/xwiki/classes and having binary files inside the /etc/ folder is a bad practice on linux.

We should try to avoid this by only linking the logback.xml files explicitly so we avoid the leaking of binary files into /etc, e.g.:
/usr/lib/xwiki/WEB-INF/classes/logback.xml -> /etc/xwiki/logback.xml