Expand schema support transforms

[terry-codecov]

Big improvement on the validator, better object validation, oneOf, started working on common custom python functions, better enum support.

Schema TODO's:

• More custom python functions to convert (such as percentage_to_number)
• Some nested object key/value pairing needs more transformation work.
• There is no descriptions script plan for custom named objects with expected pairs, this might be a v2 thing/a very late bonus if there's time

For example, default is a custom object but target, threshold, etc are validate-able but not generating descriptions yet:

  status:
    project:
      default:
        # basic
        target: auto
        threshold: 0%
        base: auto
        flags:
          - unit
        paths:
          - "src"
        # advanced settings
        branches:
          - master
        if_ci_failed: error
        informational: false
        only_pulls: false