Add crude ValidationHelper.live_validation_for_field spec.
Remove a few newlines/spaces from ValidationHelper.live_validation_for_field.

This is so it more closely matches the output from the method I intend
to use to generate it.
Make exclusion_string be generated as JSON.
Remove some whitespace in live_validation_for_field's output.

This is also for the planned rewrite that uses JSON.generate.
Make live_validation_for_field use JSON mappings.

Let's the fact that JSON is a subset of JavaScript to our advantage,
since we're generating JavaScript calls with objects and arrays.
Merge pull request #1777 from duckinator/validation-helper-cleanup

ValidationHelper cleanup