Refactor Play client to have a single executeRequest method

 - Aligns better to the underlying ning client
 - Makes it simpler to support all types of parameters consistently
   across HTTP methods
 - Paves the way to provide HTTP PATCH support in play 2.2 based on
   ning client directly in a natural way
WIP on ning client
First compiling ning client
Use JsObject instead of JsValue in execute request
Base layout for a pure ning sbt project
Remove dir where we did scratch work on ning
Add ning to client tests
Update tests based on api change in play 2 util