refactor(interchange): Simplify order books implementation (#729)

* Buy and sell order refacto

* Command changes

* Tests

* Denis

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>
Co-authored-by: Tobias Schwarz <tobias@tendermint.com>

Author: 3 people

interchain-exchange/tutorial/02-app-init.md

@@ -45,12 +45,11 @@ To scaffold two types with create, read, update and delete (CRUD) actions use th
 The following commands create `sellOrderBook` and `buyOrderBook` types. 
 
 ```bash
-starport type sellOrderBook orderIDTrack:int amountDenom priceDenom --indexed --no-message --module ibcdex
-starport type buyOrderBook orderIDTrack:int amountDenom priceDenom --indexed --no-message --module ibcdex
+starport type sellOrderBook amountDenom priceDenom --indexed --no-message --module ibcdex
+starport type buyOrderBook amountDenom priceDenom --indexed --no-message --module ibcdex
 ```
 
 The values are: 
-- `orderIDTrack` an internal counter in the order book to assign the orders an ID.
 - `amountDenom` represents which token will be sold and in which quantity
 - `priceDenom` the token selling price