Review importance of manual constraint validation

[whitlockjc]

We currently have code that will validate a defaultValue/default property (where applicable) manually in lib/validators.js. This code probably is not necessary and we should see if we can remove it and instead rely on JSON Schema validation.

[whitlockjc]

We definitely needed this code at one point and we still need to do manual validation (default values for example) but if we could create a schema to validate against, we could just defer to the JSON Schema validator for validation instead of duplicating their efforts.

[whitlockjc]

For us to remove the manual validation we would need to convert the pseudo-schema objects, like parameters, into real schemas so we can validate against the schema for said object.

[whitlockjc]

Whatever we do here, whether we keep what we have or alter it to rely on JSON Schema for validation, we should expose the method as a helper for those wanting to use it.