Householder

Updates to the householder lab.
I updated the pseudocode and solutions to fix an order of complexity issue I noticed earlier.
I also fixed spacing and clarified several different parts.

Note: this lab is long, and the Hessenberg section still needs significantly more explanation. Unless we make that section optional, this lab may take the students too much time. The coding part isn't intensive, but there is a good bit of math behind what they are doing.
The Givens lab is a bit of a stub. I'll look through it, but it seems like we could put the section on Hessenberg form there. It is a topic that lies closer to Householder reflections, but it is making this lab kind of long. We may want to consider removing it entirely.