Add initial set of settings to the recorer

[purbon]

Implements #2

[purbon]

@tsuehr thoughts? still pending the development of:

proportion_strategy = fixed / variable Default fixed. The minimum proportion of protected attributes in every prefix.

lookup_for_measuring_proportion = (integer number) Default 100. The number of top elements that are examined to determine the target proportion of protected elements.

basically to my understanding how to have the proportion inferred from the available elements, but sadly I could not find reference to this in the paper. Do you have an idea how to best determine this?

[purbon]

@tsuehr @chatox, any thoughts on this change to be merged? For me is a good first pass on settings, basically it contains what we spoke @chatox, to have the settings as query parameters, keeping the incompatible options and the only accepted values.

[chatox]

This is too detailed for me to review, sorry!