Loads classes in the following order:
1. JRE (well, actually app loader, but minus org.apache.tools.** and org.netbeans.**)
2. Ant JARs - whatever is in the "main" class loader.
3. Some NetBeans module class loader.
4. Some other JAR from $nbhome/ant/nblib/*.jar.
Used for two cases:
A. bridge.jar for #4 and the Ant module for #3.
B. ant/nblib/o-n-m-foo.jar for #4 and modules/o-n-m-foo.jar for #3.
Lightly inspired by ProxyClassLoader, but much less complex.
author: Jesse Glick