[rules-dev] ClassLoader Improvements and OSGi

[Mark Proctor]

I have done more cleaning up in the ClassLoader stuff.

While we added a root CompositeClassLoader recently there was still 
another alternative composite ClassLoader implementation that was used 
by the Packages. So we ended up with a composite CL being added to 
another CL. Both composites had their own caching etc.

So now we have  single CompositeClassLoader, with a single point of 
caching and slightly improve coding at detecting Drools specific CLs. My 
hope is that the code is also more efficient.

This work was done due to another OSGi requirement where each module 
needs to add itself to the root classloader. But sometimes it was 
returning the root CL, or sometimes the package level composite CL. So 
now there is only one and that should no longer happen.

What this means is that any module that will have it's classes resolved 
via reflection from other modules should in their constructor or other 
initialisation of the code do something like 
getRootClassLoader().addClassLoader( getClass().getClassLoader() ). In 
situations where it's a single container all modules have the same 
classloader and the call gets ignored, as it won't re-added an existing 
CL. In the OSGi case it'll add the classloader and now classes from that 
module can be resolved in an OSGi environment.

Mark