Add axiom that guarantees that L is always increases

https://github.com/linksplatform/Theory/blob/19c09c5185ab7fcd80a40cfd9f724082e7c52777/associative_proofs/net_defs.v#L24-L26

Add axiom that guarantees that L is always increases.

```coq
Variable L : Type.
Variable LS : L -> L.
Variable greater : L -> L -> bool.

Axiom LS_increases : forall n : L, greater n (LS n) = true.
```