Support `Json.valueFormat` about play-swagger

[lalnuo]

@vnt-83 This issue is about value classes.

For example, if you have following definition:

case class Foo(bar: String)

object Foo {
  implicit val jsonFormat = Json.valueFormat[Foo]
}

You can do this:

scala> Json.parse("\"foo\"").as[Foo]
val res1: Foo = Foo(foo)

However play-swagger plugin will generate api definition like this:

components:
  schemas:
    Foo:
      properties:
        bar:
          type: string

[Javakky-pxv]

@lalnuo
We are currently reviewing it. It may take some time, but we plan to address it.

[vnt-83]

Hello. I'm writing (only one) mappings for UUID like this:

- type: uuid
  specAsParameter:
    - type: string
      format: uuid

in file conf/swagger-custom-mappings.yml