Integrate population filter(s) into recipe metadata

[AARON-CLARK]

I personally like the format of the metadata layout because it is super intuitive given the layout of our dropzones. For fun, I tried to add a new table that looks like this:

"stan_0": {
    "title": "Table 0: A Fun Table Aaron like's making",
    "group_by": "TRT01P",
    "blocks": [{"data":"ADSL", "variable":"RANDFL", "statistic":"Y_FREQ"}, 
    {"data":"ADSL", "variable":"SAFFL", "statistic":"FREQ"}, 
    {"data":"ADSL", "variable":"SEX", "statistic":"FREQ"},
    {"data":"ADSL", "variable":"ETHNIC", "statistic":"FREQ"},
    {"data":"ADSL", "variable":"RACE", "statistic":"FREQ"}]
  }

It's basically just a mash up of table 3 and 5. It worked great! But what if I wanted to add a population filter to the table? I see that process is completely separate from the metadata. Is there any way we could somehow include the population config in the recipes.json file so users (like me) only have to update info in one location? What do you think about @borgmaan comment from a few weeks ago about following a ADR format?

This is where we are heading. This PR is just step one. I am just setting up the framework to allow us to accomplish this goal.

Originally posted by @AARON-CLARK in #167 (review)