Add market params notebook

[jmoreira-valory]

Add market params notebook.

This PR adds a notebook to study several parameters on the Omen markets created by the market creator:

1. Display probability distributions of number of trades per market, amount of xDAI spent per trade, and consistency of the most traded option (i.e., what is the % of the most voted option on a given market)
2. Simulate FPMMs and study the outcome probability of the market simulations based on a number of configuration parameters (number of trades, amount per trade, mech consistency, fee, etc.)

This PR does not modify the logic of the market creator.