Parameter/override tutorials

* Adds necessary parameter and override features to chatter_concert.
* Removes overrides tests from concert_tutorials (I want to deprecate this eventually)
* All three tutorials now have a solutions folder which contains the necessary **solution bundle**.

Note the second point - let's put all our new tests/features in chatter and turtle, simply because I hardly ever actually *run* and thus test the concert tutorial (it's extra overhead for me).