Add the outcome label to the DB

[AntonioPMCS]

Right now, outcomes are merely seen as positions in the outcomes array. There is a matching between position [0, No] and [1, Yes]. This is arbitrary and is enforced throughout the code and as a constant definition.

This is a bit of a limitation and might cause some confusion in questions where the outcome might not be "Yes" or "No". For example: "Who will win the 2022 world cup. Siberia or Kazaquistan?"

In case it is desired to expand the semantic possibilities for writing a question, it is necessary to dynamically map outcome indexes to an arbitrary English word. This relationship can be stored at the data layer level (for example in the database), as part of the market identity.