Some major changes here.

Restructured the 'axis/plugins' folder (We should only have core plugins here. All custom and provider plugins should be located in a 'zone' folder).

Refactored plugin structure. Now all plugins need to be PSR-0 compliant (namespace/classes can now be autoloaded without plugin devs having to do so manually). This raises the learning curve, but it doesn't make sense for the rest of the system to be PSR-0 compliant, while plugins mix code that declares new symbols with code that causes side-effects. I also believe it will open up more opportunities and flexibility when it comes to plugin development.