Add overrides and defaults for agnosticv-operator

[jkupferer]

Add support for agnosticv-operator to declare overrides and defaults.

Ex:

spec:
  defaults:
    __meta__:
      access_control:
        allow_groups:
        - rhpds-admins
  overrides:
    __meta__:
      anarchy:
        namespace: babylon-anarchy-{{ (asset_uuid | uuid2int) % 8 }}

[fridim]

need functional tests to ensure its does what it's supposed to?