Provide anyParams that was available in Spray

As documented in: http://spray.io/documentation/1.1.4/spray-routing/any-param-directives/anyParams/

Original impl here: https://github.com/spray/spray/blob/b473d9e8ce503bafc72825914f46ae6be1588ce7/spray-routing/src/main/scala/spray/routing/directives/AnyParamDirectives.scala

This will require shapeless though - or a "mini shapeless" so we should think where / how to put it.

Would be a very cool one to contribute by the community if someone wants to play around as type astronaut 😉

Start with the Spray anyParams documentation and the original AnyParamDirectives.scala implementation linked in the issue. Investigate how the equivalent directive should fit into akka-http and whether shapeless or a smaller substitute is appropriate. Done means an akka-http implementation matching the documented Spray behavior, with the dependency or substitute decision resolved.

Written by the indexing model from the issue text.