Changed executeComponent() to use the factory method of JController (see pull request #193 )

Changed executeComponent() to use the factory method of JController. The parameter $baseClass is added, and passed by renderComponent().

See discussion "Object oriented components , any plan?"
https://groups.google.com/forum/?fromgroups#!topic/joomla-dev-cms/7tjVkzc08Ks


Change-Id: Ie19778dddc492814dc549c54f1a7c45cf80404c3