Swagger integration

What do you think about adding action for generation api-docs. I implement SwaggerDocAction for Swagger-UI. It is collect all routes with @SwaggerDoc annotation and generate /api-docs.json which can be used in swagger-ui to display api documentation.

For example, in our project documenting looks like:
```
@GET("organization/:respondType")
@SwaggerDoc(summary = "Full text search for organizations",
  parameters = Array(
    new SwaggerParameter(name = "town", typename = "int", description = "List of town ids to search",
        required = true, allowMultiple = true),
    new SwaggerParameter(name = "query", typename = "string", description = "Full text search query", required = true),
    new SwaggerParameter(name = "doctype", typename = "string", description = "Type of result document", required = true),
    new SwaggerParameter(name = "limit", typename = "int"),
    new SwaggerParameter(name = "offset", typename = "int")))
class OrganizationSearch extends APIAction {
  import CatalogConfig._

  def execute {
    val towns = params[Long]("town")
    val query = param("query")
    val docType = param("doctype")

    val organizations = FTS.organization(query, towns)
    val request = requestForDocument(organizations, docType, respondType)
    val response = WS.prepareGet(request).execute.get

    respondText(response.getResponseBody, response.getContentType)
  }

}
```