A new chapter structure

[MHenderson]

Chapters 4 and 6 are just too short and should probably be incorporated into chapters 3 and 5.

Chapter 2 could be replaced with a chapter describing methods of constructing Room squares. We could introduce the naive greedy approach which gives rise to maximal partial Room squares and also move the starter-adder construction to this new chapter.

[MHenderson]

Summat like this:

1. Preliminaries: graphs, BIBDs
2. Introduction
3. Starters, adders and cyclic Room squares
4. Strong starters (inc. Mullin-Nemeth)
5. The trouble with Fermat numbers?
6. Multiplication of Room squares
7. An existence theorem for Room squares
8. Balanced Room squares
9. Complete balanced Room squares
10. Multiplication of balanced Room squares.
11. A graph theoretic approach
12. Hill-climbing algorithm

[MHenderson]

First do #164