Classloader improvements

[LukeTowers]

Requires wintercms/storm#72

[what-the-diff]

• The parent::register() method was added to the register methods of all modules.
• A call to autoloadPackage($namespace, $path) was added in PluginManager's loadPlugin function for each plugin that is loaded by the system module. This allows plugins and their classes to be auto-loaded without having a composer package definition file (composer.json).
• All module and plugin files are manually registered with Composer's ClassLoader class so they can be auto-loaded when needed during runtime execution of OctoberCMS codebase functions/methods/classes etc...