support @JsonIgnoreProperties annotation

[zyro23]

seems @JsonIgnoreProperties on model classes is currently ignored.

springfox/springfox#113 suggest to use @JsonIgnore instead.

however, in grails, command objects usually implement the Validateable trait that adds a getErrors() method. but you cannot annotate that getter with @JsonIgnore because it is injected by the trait at compile time. my common swaggered grails command object (using swagger-servlet, not springfox) looks like:

@JsonIgnoreProperties("errors")
class MyCommand implements Validateable { ... }

[dilipkrish]

@zyro23 thanks for reporting issues. This is great feedback!

[dilipkrish]

@zyro23 addressed via fixing #6