avoid use of hlevel of functions for now
Adding stuff on equivalences.
switched from hlevels to n-types, according to wishes expressed by others
worked on introduction
Remove \includeonly in main
Computing with binary cartesian product types
changed forgotten occ of isofhlevel to n-type
worked on introduction
worked on introduction
small fixes to Sigma-types
Pi-types in basics
fixes to Pi
Added proofs for equivalences.
Added derivation of PM identity elimination.
Move adjointification to Chapter 3
basics: the unit type, and an introduction to sets