re-implemented theme watch tasks, add parallel tasks, added ability to c...

...reate dynamic parallel targets
The only thing that this option gets you is a simplified way to generate your own parallel target that includes existing tasks and ones you define yourself without having to write the Gruntfile. But as you point out, the syntax for the Gruntfile itself is not significantly more complex and probably doesn't justify the extra work. Again, I can just remove it for the sake of keeping GDT lean.