Class Autoloading

To explore this idea (from my previous post), I've pushed the 
classrename scenario, which renames the classes in the DD module, more 
or less along the lines of the PEAR naming scheme (name reflects the 
folder hierarchy the class is in).

I'm no big fan of long underscored class names, but I think the tradeoff 
is worth it in this case. Over a hundred sys::imports were removed, 
along with a cluster of files which were basically doing nothing but 
making sure some classes were imported.

Granted some of this may have been past sloppiness, but the point is 
that using the autoload mechanism automatically ensures that only what's 
actually needed is loaded. Like the consistent use of interfaces, saves 
us from ourselves.

Extending this to other modules is straightforward, since by convention 
the modules all have their classes in the "class" folder. In the case of 
the core it's less clear where the disadvantages begin to outweigh the 
benefits, as the class structure of the core is not as homogeneous and 
simple as that of the modules.