I am torn between closevoting as too localized and wanting to comment on the code. Also, it's too much code to wade through now, so I will comment only a few things:
1) Documentation style
Why not use an established documentation format, like PHPDoc?
2) Formatting
is consistent as far as I can see, but I suggest to use a coding convention that is in wide use, like that of PEAR or ZF (which is based on PEAR) instead of doing your own (yours is close to PEAR anyway, so you might as well adopt it completely).
3) Singleton pattern
In order for the Singleton to work it has to have a private __contruct and __clone method. But I suggest not to use it at all. Many people believe the Singleton is an AntiPattern. There are a number of questions on SO discussing the disadvantages of the Singleton pattern, so have a look around. If there should be only one instance, then simply dont instantiate a second one. If you need to access the FrontController in other classes, inject it.
4) Method length
I probably would try to shorten the dispatch
method. Basically, if you describe what a method does and you have to use an and to do so, that part should go into it's own method. Try to make methods into small discrete units. That will make UnitTesting easier as well.
5) Separation of Concerns
I am not sure why the FrontController extends from ActionController. There is no other classes that extent it, butI suppose the classes the FrontController instantiates are subclasses of ActionController too. But the FrontController, while named a controller, does different things than the PageControllers, so I'd probably keep them separated.
On a sidenote, if you are interested in increasing the quality of your code, have a look at the slides and tools given at http://phpqatools.org/