bake from controller

Very basic.
Only does "cake bake [type] [model]".
No interactive mode, but still a time saver, just needs to be fleshed
out, but it's a starting point.

The main issue was that although you can run a shell from a controller,
you can't run bake because there is no $argv, so you just have to pass
in your arguments manually, and add a parameter for the ShellDispatcher
so that it doesn't call bootstrap() again, else the core freaks out.

My reasoning behind my addition is that it's a very small code change
that opens a door for core functionality, makes it easier for less
experienced devs to get into Cake, lets you create a backend where you
can build as you go, and should you be pressed for time, and not be able
to set up your environment nicely or for some reason can not access a
command line, you can just bake from a controller.
why return mixed now?