Remove usage of p-chains and l-chains
Convert usages of p-chains and l-chains to just chains
rho ≡ 0 between two points implies the points are equal
Cosmetic changes to ChainsWithProp
Simplify ChainsWithPropertySetoid greatly

Use propositional equality of chains directly
First claim of Lemma 2.4

m 0 r = delta 0 r