Field equality

I find that overly restrictive access controls often cause more pain than they solve. In Maestro it is quite clear what we expose as the canonical API and what is under the hood.

In this particular case Field is just a custom getter part of a lens. It seems like it would be nice for users to be able to define their own custom lenses that are kind of similar to what we provide via macros which is what makes me hesitant to make field private.

The Load, Field, Tag, Clean, Splitter part of the API is due for a significant refactor, where we can address some of those issues. However, we should bed down the Execution stuff first before we tackle this so in the mean time we will have to tackle this ugly approach before we can do the structural fixes that are needed.