Remove JSON-Viewer from Proposed Schema display

[acrosman]

Summary
JSON-Viewer is slow, and causes problems for large schemas -- it should be removed.

Please describe the problem you are trying to solve.
JSON-Viewer takes a long time to render large objects, and the interface more-or-less locks while that runs. What's more the display isn't all that useful either.

Proposed Solution
Remove JSON-Viewer from the display of the schema. Offer a shorter, and more efficient, summary of the tables about to be generated.

[acrosman]

We could instead generate a list of tables using an Accordion layout with each section holding list of the fields and their types. It might be possible from there to then more easily add object and field level editing (something that is useful in some use cases).