Added tooling for null columns JSON files

[antoniocarlon]

• Added a tool to build column restrictions JSON files from an ETL log file
• Added a tool to merge two different column restrictions JSON files

[antoniocarlon]

@javitonino thank you for the suggestions :hugs: I think I have addressed all of them. Second CR round?

[juanignaciosl]

Tooling FTW :heart:

@javitonino I guess that this can be merged after your CR suggestion, right?

[javitonino]

Yup, it should be ready to rock.