Refactor the way how loopback types are converted to swagger data types.
- `modelHelper.LDLPropToSwaggerDataType` is responsible for
producing a valid Swagger Data Type object from LDL object
(be it a property, accepts item or returns item).
- LDLPropToSwaggerDataType picks only fields that are part
of the swagger spec, everything else is excluded from the result.
It's up to the caller to add extra fields like `description`.
- refactor `routeHelper.extendWithType` to accept an additional arg:
the original LDL object. This way it's possible to copy all
type-specific fields to the output object and don't add anything
else.
Miroslav Bajtoš
Krishna Raman
Samuel Reed