TMI: Refactoring

Today I more or less only worked on #4678, and I finally got stage1 to compile! Of course, it doesn't work yet. So far, I've changed the ty param list in a trait item to be a non-empty list, so that it's obvious which param is the self type parameter. That's the point of the issue, making the Self type in a trait just like any other type parameter (because that's what it is, and this gets rid of some needless code). But, I haven't updated resolve yet to resolve the Self type to the first ty param. At least my build's failing in the way I expect it to.

And, unbelievably, I'm not done with one-tuples either; I got the compiler to compile and the whole test suite to pass except... the one test case that I added for one-tuples, which fails to parse in the exact same way it did in the first place. sadtrombone.wav