ClassLoaderPlus: sort problematic fat jars last

We want JARs like jython, jruby and batik to be deprioritized when
loading classes, because these JARs contain older and
known-to-be-broken-and-incompatible classes, particularly for XML
packages such as org.apache.xpath. Joda time is another example.

Concocted with excellent help from Johannes Schindelin.