Spike on improvements to Form Builder

[lkogler]

The goal is to understand how best to move forward with improvements to the Form Builder.

• What would be the level of effort / complexity that would be required to extract the GCF form builder into Honeycrisp?
• How could we create a more consistent / flexible interface for the form builder?

[hartsick]

A thing about the interface we'd like to change: require label_text and legend_text for all methods. We think we realistically won't use the Rails default fallbacks for labels, which was the motivation for making them optional.

[hartsick]

Closing in favor of #124