Add flexible field management

[francbartoli]

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[francbartoli]

@darothen I'd rather you have a look before having this merged. Thanks!

[darothen]

I think I understand what you're going for here, but do you think you could make a quick notebook or gist to illustrate the use case?

At a minimum, we should think about making the default nofield case a bit easier to work with. Part of the philosophy with Experiment is that if something is simple/common/straightforward, you don't have to do much (anything, really) for it to work. The same should extend to the idea of a Field.

[francbartoli]

@darothen maybe the use of Field in the sample script is enough for now?