PluginLoader cleanup
PluginLoader cleanup

- Added Zend\Loader\ShortNameLocater
- s/Zend\Loader\PluginLoader\PluginLoaderInterface/Zend\Loader\PrefixPathMapper/
  Extends Zend\Loader\ShortNameLocater
- s/Zend\Loader\PluginLoader\PluginLoader/Zend\Loader\PluginLoader/
  Implements Zend\Loader\PrefixPathMapper
- s/Zend\Loader\PluginLoader\Exception/Zend\Loader\PluginLoaderException/
- Updated all classes and tests to reflect the above

MadCat34/zend-feed