Qr2

I marked multiple %TODO's in this lab:

- Most (all?) of the data is made-up. For the least squares problems, the data looks made-up. It especially looks too close to the lines it is supposed to fit. I think we should at least make up more realistic-looking data. Better still would be to find some real data.

- There are some issues with the QR factorization and the least squares problem in the lab. That problem is a good problem, and I think we should keep it, but it will probably need to be rewritten once the QR presentation in the text is finalized.