Move observer calls to respective tables

Moving the calls to create the observer from the cms.php file to the proper tables.

This is done so the code is better understandable by 3rd party extension developers trying to figure out how tags work. Also there is no need to decouple these calls, as the data is tightly coupled anyway. The observers need to be there in this case or we may loose data.

I also had to move the oberserver interfaces and classes to their own files so the autoloader will find them. The problem was that once I removed the JObserverMapper calls from cms.php, the JTable class would not find the JObservableInterface anymore.